Research progress on regulation of gut microbiota abundance induced by ambient particulate matter exposure / 环境与职业医学

Particulate matter (PM) is the main air pollutant in China. Due to its wide distribution and difficulties in control, PM has been widely concerned. PM mainly enters human body through respiratory exposure and can cause a variety of health problems. Recent studies have shown that PM exposure is also associated with the occurrence and development of digestive system diseases, as it can enter human body indirectly through the respiratory tract or directly through the digestive tract. Gut microbiota (GM) is a group of microorganisms located in the intestinal epithelium mucosa and intestinal lumen. GM is large in number and rich in functions, and its homeostasis plays an important role in the intestinal health of individuals and even the health of the body. Because GM may mediate the health effects induced by environmental factors, more and more studies have focused on the effects of ambient PM on GM. In this review, we summarized the effects of a variety of ambient PM on GM homeostasis, focusing on five major phyla including Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Verrucomicrobia, and discussed their main functions and the effects of PM on their homeostasis and abundance.

Antibacterial activity of Nocardia spp. and Streptomyces sp. on multidrug-resistant pathogens causing neonatal sepsis

ABSTRACT Neonatal sepsis leads to severe morbidity and occasionally death among neonates within the first week following birth, particularly in low- and middle-income countries. Empirical therapy includes antibiotics recommended by WHO. However, these have been ineffective against antimicrobial multidrug-resistant bacterial strains such as Klebsiella spp, Escherichia coli, and Staphylococcus aureus species. To counter this problem, new molecules and alternative sources of compounds with antibacterial activity are sought as options. Actinobacteria, particularly pathogenic strains, have revealed a biotechnological potential still underexplored. This study aimed to determine the presence of biosynthetic gene clusters and the antimicrobial activity of actinobacterial strains isolated from clinical cases against multidrug-resistant bacteria implicated in neonatal sepsis. In total, 15 strains isolated from clinical cases of actinomycetoma were used. PCR screening for the PKS-I, PKS-II, NRPS-I, and NRPS-II biosynthetic systems determined their secondary metabolite-producing potential. The strains were subsequently assayed for antimicrobial activity by the perpendicular cross streak method against Escherichia fergusonii Sec 23, Klebsiella pneumoniae subsp. pneumoniae H1064, Klebsiella variicola H776, Klebsiella oxytoca H793, and Klebsiella pneumoniae subsp. ozaenae H7595, previously classified as multidrug-resistant. Finally, the strains were identified by 16S rRNA gene sequence analysis. It was found that 100% of the actinobacteria had biosynthetic systems. The most frequent biosynthetic system was NRPS-I (100%), and the most frequent combination was NRPS-I and PKS-II (27%). All 15 strains showed antimicrobial activity. The strain with the highest antimicrobial activity was Streptomyces albus 94.1572, as it inhibited the growth of the five multidrug-resistant bacteria evaluated.

Antimicrobial activity of two Antarctic Streptomyces strains

Aims@#The search for new antibiotics is an ongoing effort and has expanded to pristine niche areas in the Antarctic in recent years due to the emergence of multi-drug resistant pathogens that outpaced the discovery of new antibiotics. We have recently isolated two new actinomycetes strains, INACH3013a and INACH3013b, which displayed antimicrobial properties from soil samples collected from Ardley Island, Antarctica. Hence, an investigation was carried out to identify them and to characterise the antimicrobial compounds produced.@*Methodology and results@#Strains, INACH3013a and INACH3013b were identified based on their 16S rDNA sequence alignment to those in the GenBank. The results showed that strain INACH3013a was closest to Streptomyces spp. while strain INACH3013b was closest to Streptomyces corallincola and Streptomyces bullii. The extracellular compounds they produced were extracted using various solvents and the extracted compounds were tested against the test pathogens. The dichloromethane extracts from strains, INACH3013a and INACH3013b inhibited mainly Gram-positive pathogens that include Listeria monocytogenes, Staphylococcus aureus, Staphylococcus haemolyticus, Staphylococcus equorum, Bacillus cereus K3 and Enterococcus faecalis while extracts from strain INACH3013b also inhibited a Gram-negative pathogen, Klebsiella pneumonia 14x. Predominantly non-polar constituents seem responsible for antibacterial effects, with dichloromethane extracts proving most efficacious, followed by chloroform and ethyl acetate. @*Conclusion, significance and impact of study @#The research highlights the potential of Streptomyces spp. INACH3013a and INACH3013b as a source of potential novel antibiotics. This research explores Antarctic Streptomyces strains' antimicrobial capabilities, enabling the potential for the discovery of novel antibiotics and revealing how these compounds may have helped them to compete and survive in nutrient-deficient Antarctic niches.

Protease inhibitors as a potential agent against visceral Leishmaniasis: A review to inspire future study

Abstract Leishmaniasis is transmitted by sandfly which carries the intracellular protozoa in their midgut. Among visceral, cutaneous and mucocutaneous leishmaniasis, visceral type that is caused by Leishmania donovani is the most lethal one. Findings of leishmanial structure and species took place in 19th century and was initiated by Donovan. Leishmaniasis is still a major concern of health issues in many endemic countries in Asia, Africa, the Americas, and the Mediterranean region. Worldwide1.5-2 million new cases of cutaneous leishmaniasis and 500,000 cases of visceral leishmaniasis are reported each year. Leishmaniasis is endemic in nearly 90 countries worldwide and close to 12 million new cases of leishmaniasis are reported worldwide annually. Studies on antileishmanial drug development is of major concern as leishmaniasis are the second largest parasitic killer in the world and the available drugs are either toxic or costly. The major surface GP63 protease, also known as Zinc- metalloproteases present on the surface of leishmanial promastigotes, can be targeted for drug development. Protease inhibitors targeting such surface proteases show promising results. Different protease inhibitors have been isolated from marine actinobacteria against many infectious diseases. Metabolites produced by these actinobacteria may have greater importance for the discovery and development of new antileishmanial drugs. Hence, this review discusses the background, current situation, treatment, and protease inhibitors from marine actinobacteria for drug development against GP63 molecules.

Microbial evaluation of implant surface - a clinical study comparing submerged, non-submerged and immediately loaded implants

Aim: The aim of the present study was to evaluate the microbial contamination in internal and external walls of cone morse implant walls. Methods: Eleven patients with edentulous mandibular posterior area were selected to received dental implants, divided into groups: submerged (S), non-submerged (NS), and immediately loaded (IL). Microbiological evaluations (microorganisms' number, aerobic and anaerobic colony forming units (CFU) number and microorganisms' qualification) were divided into internal and external collection of the implant walls, at different stages: T0 (surgical procedure), T2 (suture removal), T4 (reopening S group), T6 (suture removal S group), and T8 (abutment placement in S and NS). All data were submitted to statistical analyses, with confidence level of 0.05. Results: There was difference in number of microorganisms observed over time within the same group (p < 0.05). A difference was observed in CFU when evaluated within the same group over time (p < 0.05), except for the IL group. In internal collection, a predominance of non-formation of microorganisms was observed at T0 in all groups, while formation of Gram-positive Diplococci and Gram-positive Bacilli was observed at T8 (p>0.05). In external collection, an increase in number of microorganisms was observed at T0. Conclusion: There was no difference in microbial contamination among the evaluated groups. The microorganism's colonization changed over time

Antimicrobial, antioxidant and anticancer potential of Streptomyces species isolated from the rhizosphere of Avicennia marina (Forssk.) Vierh

Free radicals produced through biochemical processes cause dangerous health problems due to their oxidative effect on cellular proteins and lipids. There is an urgent need for natural antioxidants to be used as therapeutic agents. Streptomyces are known as producers for antioxidants, in this study, two Streptomyces species were isolated from the rhizosphere soil of mangrove tree Avicennia marina (Forssk.) Vierh. The isolates were identified by conventional as well as molecular methods as Streptomyces atrovirens (MS5) and S. labedae (MR15). The ethyl acetate extracts of cell free production broth medium of the two isolates demonstrated potent biological activities against Gram positive and Gram negative bacteria and Candida albicans. Moreover, a radical scavenging activity in DPPH assay with significant inhibition percentage of 62 and 78%, respectively, was recorded. The IC50 values were 3000 and 241 ?g/mL (P <0.05) for S.atrovirens (MS5) and S. labedae (MR15), respectively. Streptomyces atrovirens extract showed anticancer activity against hepatocellular carcinoma cells (HepG-2) and colon carcinoma cells (HCT-116) cell lines with 61 and 50.6%, respectively, while S. labedae (MR15) showed anticancer activity against all the tested cell lines with 92.9 and 85.89% against (HepG-2) and (HCT-116) compared to the control cells and showed selective cytotoxicity. LC-MS/MS analyses revealed the presence of compounds with known antioxidant and anticancer activities such as Gamma Aminobutyric acid (GABA) and Indole-3-carboxyaldehyde, linoleic acid and phenyl chromen-4-one derivative with various intensities.

Barrientosiimonas humi ethyl acetate extract exerts cytotoxicity against MCF-7 and MDA-MB-231 cells via induction of apoptosis and cell cycle arrest

@# Objective: To elucidate the cytotoxic effect of the secondary metabolites of Barrientosiimonas humi (B. humi) on MCF-7 and MDA-MB-231 human breast cancer cells and its underlying mechanisms of action. Methods: The extract was obtained from the fermentation of B. humi and fractionation of the crude extract was conducted via column chromatography. Cytotoxicity of the B. humi extract was determined by using MTT assay and real-time cellular analysis. Morphological changes, cell cycle profiles, mode of cell death, and caspase expressions of control and treated breast cancer cells were determined. Results: The ethyl acetate extract isolated from B. humi was cytotoxic against MCF-7 and MDA-MB-231 cell lines. One of the dichloromethane (DCM) fractions, designated as DCM-F2, exhibited the strongest activity among all the fractions and thereby was selected for further studies. DCM-F2 had selective cytotoxicity on target cells by inducing apoptosis, particularly in the early stage, and cell cycle arrest. Treated cells caused inhibition of cell cycle progression at 72 h leading to a significant increase (P < 0.05) in the G0/G1 population. DCM-F2 treated MDA-MB-231 cells showed caspase-dependent apoptosis, whereas DCM-F2 treated MCF-7 cells showed a caspase-independent apoptosis pathway. Five compounds were successfully isolated from B. humi. Cyclo (Pro-Tyr) was the most cytotoxic and selective compound against MCF-7 cells. Conclusions: B. humi ethyl acetate extract exhibits significant cytotoxicity against MCF-7 and MDA-MB-231 cells via induction of apoptosis and cell cycle arrest.

Changes in freshwater sediment microbial populations during fermentation of crude glycerol

BACKGROUND: This work studied how the exposure to an unusual substrate forced a change in microbial populations during anaerobic fermentation of crude glycerol, a by-product of biodiesel production, with freshwater sediment used as an inoculum. RESULTS: The microbial associations almost completely (99.9%) utilized the glycerol contained in crude glycerol 6 g L 1 within four days, releasing gases, organic acids (acetic, butyric) and alcohols (ethanol, n-butanol) under anaerobic conditions. In comparison with control medium without glycerol, adding crude glycerol to the medium increased the amount of ethanol and n-butanol production and it was not significantly affected by incubation temperature (28 C or 37 C), nor incubation time (4 or 8 d), but it resulted in reduced amount of butyric acid. Higher volume of gas was produced at 37 C despite the fact that the overall bacterial count was smaller than the one measured at 20 C. Main microbial phyla of the inoculum were Actinobacteria, Proteobacteria and Firmicutes. During fermentation, significant changes were observed and Firmicutes, especially Clostridium spp., began to dominate, and the number of Actinobacteria and Gammaproteobacteria decreased accordingly. Concentration of Archaea decreased, especially in medium with crude glycerol. These changes were confirmed both by culturing and culture-independent (concentration of 16S rDNA) methods. CONCLUSIONS: Crude glycerol led to the adaptation of freshwater sediment microbial populations to this substrate. Changes of microbial community were a result of a community adaptation to a new source of carbon.

Cytotoxic activity of methanolic extract of Streptomyces sp. strain KSF 83 on growth of human breast and colon cancer cells

Aims@#The attention for new and effective anticancer drugs but less toxic is increasing over time. Streptomyces is the most important and well-known source of their bioactive compound production with useful bioactivities. This work aimed for evaluation of the anticancer potential of methanolic extract of Streptomyces sp. strain KSF 83 against non-cancerous cell lines (CCD-841-CoN), breast (MCF-7, MDA-MB-231) and colon cancer cell lines (HT-29, HCT-116).@*Methodology and results@#The characteristic of the strain KSF 83 was identified by morphology and 16S rRNA sequencing and results confirmed that the strain belonged to the genus of Streptomyces. The crude substance was produced via submerged fermentation from the strain and methanol solvent was used to extract the culture filtrate. Methanolic extract possessed low toxicity against CCD-841-CoN with only 18% of inhibition activity at the 400 µg/mL. Among all tested cancer cells, the methanolic extract was able to inhibit the growth of all cancer cells tested with MCF-7 was the highest anticancer activity recorded. The methanolic extract also exhibited cytotoxicity in a range of EC50 of 65.79 μg/mL to 262.40 μg/mL. This study revealed the anticancer potential of Streptomyces sp. strain KSF 83, which could be sources of prospective anticancer drugs against breast and colon cancer.@*Conclusion, significance and impact of study@# The extract of KSF 83 was non-toxic toward normal cell lines and able to inhibit the growth of breast and cancer cell lines, thus it can be a potential source of the anticancer drug against breast and colon cancer.

Diversity,novelty,antimicrobial activity,and new antibiotics of cultivable endophytic actinobacteria isolated from psammophytes collected from Taklamakan Desert / 药物分析学报

Three hundred and twenty endophytic actinobacterial strains were isolated from psammophytes collected from Taklamakan Desert and identified.Among them,three strains already had been identified as new species of two genera and sixteen isolates showed relatively low 16S rRNA similarities＜98.6％to validly described species.Seventy-five of the isolates were selected as representative strains to screen antibacterial activity and mechanism.Forty-seven strains showed antagonistic activity against at least one of the indicator bacteria.Two Streptomyces strains produced bioactive compounds inducing DNA damage,and two Streptomyces strains produced bioactive compounds with inhibitory activity on protein biosynthesis.Notably,the strain Streptomyces sp.8P21H-1 that demonstrated both strong antibacterial activity and inhibitory activity on protein biosynthesis was prioritized for exploring new antibiotics.Under the strategy of integrating genetics-based discovery program and MS/MS-based molecular networking,two new streptogramin-type antibiotics,i.e.,acetyl-griseoviridin and desulphurizing gri-seoviridin,along with known griseoviridin,were isolated from the culture broth of strain 8P21H-1.Their chemical structures were determined by HR-MS,and 1D and 2D NMR.Desulphurizing griseoviridin and griseoviridin exhibited antibacterial activities by inhibiting translation.

Identification and antimicrobial activities of Streptomyces, Micromonospora, and Kitasatospora strains from rhizosphere soils

Rhizosphere soils are the major habitat of various bacteria, especially the actinobacteria. In this study, 17 actinomyceteswere isolated from rhizosphere soil samples collected from the plants, including Barringtonia racemosa, Albizziaodoratissima, Spondia spinnata, and Azadirachta indica. On the basis of 16S rRNA gene analysis (99.0%–100%similarity), the isolates were belonged to genera Streptomyces (10 isolates), Micromonospora (5 isolates), andKitasatospora (2 isolates). They were identified as Streptomyces sioyaensis (2 isolates), Streptomyces vietnamensis(2 isolates), Streptomyces bungoensis (2 isolates), each of Streptomyces psammoticus, Streptomyces purpurascens,Streptomyces hydrogenans, Streptomyces lucensis; Micromonospora schwarzwaldensis, Micromonospora chersina,Micromonospora terminalae, Micromonospora chaiyaphumensis, Micromonospora rhizosphaerae and two isolatesas Kitasatospora putterlickiae. On the results of antimicrobial activities, three isolates presented the good activitiesagainst Candida albicans ATCC 10231, and Escherichia coli ATCC 25922, while 10 isolates exhibited the goodactivities against Staphylococcus aureus ATCC 25923 and 11 isolates exhibited activities against Bacillus subtilisATCC 6633. Among them, JA03 showed 98.95% similarity of 16S rRNA gene sequence to S. psammoticus NBRC13971T, this isolate might be the novel species of actinomycetes

Determination of the biodegradability of chitosan utilizing the most probable number technique

The present work aimed to evaluate the degradability of the chitosan polymer by soil microorganisms.This evaluation was accomplished using the Most Probable Number (MPN) method by plating in drops so that soil microorganisms capable of degrading the polymeric material could be quantified. Soil samples diluted in three specific culture media for each typeof microorganism were plated –bacteria, fungi and actinobacteria–and they were maintained at 28°C for seven days to determine the growth rate of fungi and actinobacteria, and for 48hoursfor the development of bacteria. Significant differences in the MPN of actinobacteriarelative to the other groups analyzed were observed. Thus, the method used was effective for determining the degradability of the chitosan biopolymer when observing the development of microorganisms subjected to the replacement of thecarbonsource by the addition of 2% w v-1of the chitosan biopolymer to the culture medium. The formation of clear regions around the microbial colonies was a strong indicator of biodegradation.

Identification and antibacterial activity of three mangrove-derived Streptomyces / 中国药理学通报

Aim To study and identify the antibacterial activity of three strains of Streptomyces (K57M, K51M, K131M) collected from the roots of mangrove rhizosphere in Maowei Sea, Guangxi. Methods Acti-nobacteria were isolated on four media and purified by ISP2 medium. The 16S rRNA gene sequences of three actinobacteria strains were obtained by PCR amplification and sequencing. Sequences of 16S rRNA gene obtained by PCR amplification were submitted to gene database for BLAST search. Phylogenetic tree was constructed by adjacency method, and homology analysis was carried out to study the diversity and novelty of actinobacteria. Three actinobacteria strains underwent primary screening using Oxford cup method, and the antimicrobial activity of the sample of El-3, AI-3 and Ml-3 received secondary screening using disk diffusion method. Results Sequence alignment analysis of 16S rRNA gene revealed that strain K57M might be a potential new actinobacteria. The results of screening for antimicrobial activity showed that three strains of Streptomyces, K57M, K51M and K131M, had good antimicrobial activities against different drug-sensitive strains. Conclusions Streptomyces from rhizosphere in the roots of mangrove forests in Guangxi can produce strong antibacterial activities, which provides great possibilities to explore natural active antibiotics.

Mycobacterium genus and tRNA arrays

The presence of tRNA array, a region with high tRNA gene number and density, has been demonstrated in Mycobacterium genus. However, a recent phylogenomic study revealed the existence of five distinct monophyletic groups (genera) within this genus. Considering this new scenario, and based on in-silico analyses, we have identified and characterised the abundance and diversity of tRNA array units within Mycobacterium, Mycolicibacterium gen. nov., Mycolicibacillus gen. nov., and Mycobacteroides gen. nov. The occurrence and prevalence of tRNA arrays among the genera belonging to Actinobacteria indicate their possible role in the organismal fitness.

Composition of bacterial community in enrichment cultures of shale by-products from Irati Formation, Brazil

ABSTRACT We examined microbial communities from enriched fine and retorted shale particles using sequencing of V4 variable region of 16S rRNA. High number of microbial genera was found in both enriched shale by-products that were dominate by Actinobacteria, Firmicutes and Proteobacteria, showing differences due to microbial colonization after the pyrolysis process.

Actinomicetos con actividad anti-candida aisladas de hormigas cortadoras de hojas Atta cephalotes (Formicidae: Myrmicinae: Attini) / Actinomyces with anti-candida activity isolated from leaf-cutting ants Atta cephalotes (Formicidae: Myrmicinae: Attini)

RESUMEN Objetivos. Aislar, seleccionar e identificar actinomicetos asociados a hormigas cortadoras de hojas Atta cephalotes (Linnaeus, 1758), que presenten mayor actividad anti-Candida. Materiales y métodos. Estudio transversal realizado en hormigas recolectadas de una localidad de Huánuco, Perú, a partir de las cuales se aislaron cepas de actinomicetos que fueron evaluadas mediante pruebas in vitro para determinar su capacidad antagonista frente a especies de Candida. Los actinomicetos de mayor antagonismo fueron seleccionados y cultivados en agitación, luego se obtuvieron los metabolitos extracelulares con solventes orgánicos y finalmente se evaluaron los extractos crudos para determinar cuantitativamente la concentración mínima inhibitoria (CMI). Resultados. Se logró aislar 30 actinomicetos, de los cuales el 47 % presentaron actividad antagonista a Candida albicans (C. albicans) ATCC 7516, el 43 % a Candida parapsilosis ATCC 7307, el 37% a Candida tropicalis ATCC 7206 y C. albicans ATCC 10231 y el 30% a C. albicans ATCC 98028. Extractos orgánicos de las cepas HAA-16 y HAA-17 presentaron marcada actividad anti-Candida; siendo el extracto de acetato de etilo de la cepa HAA17 el de mejor rendimiento por tener mayor espectro de actividad y presentar una CMI de 3,25 mg/ml frente a C. albicans ATCC 7516 y Candida parapsilosis ATCC 7307. Los actinomicetos seleccionados se identificaron mediante técnicas moleculares como miembros del género Streptomyces. Conclusiones. Los actinomicetos asociados a Atta cephalotes son excelentes productores de compuestos bioactivos, capaces de inhibir el crecimiento de levaduras patógenas del género Candida y con potencial aplicación en el desarrollo de nuevos productos naturales de interés biomédico.

ABSTRACT Objectives. To isolate, select and identify actinomyces associated to leaf-cutting ants Atta cephalotes (Linnaeus, 1758), that present a greater anti-Candida activity. Materials and Methods. Cross-sectional study made with ants collected at a location in Huánuco, Peru, from which strands of actinomyces were isolated and later evaluated by in vitro testing in order to determine its antagonistic capacity against species of Candida. The actinomyces with greater antagonism were selected and cultured by agitation, then the reliable extracellular metabolites were obtained with organic solvents, and finally the crude extracts were evaluated to determine quantitatively the minimum inhibiting concentration (MIC). Results. Thirty (30) actinomyces were isolated, of which 47% exhibited antagonistic activity against Candida albicans (C. albicans) ATCC 7516, 43% to Candida parapsilosis ATCC 7307, 37% to Candida tropicalis ATCC 7206 and C. albicans ATCC 10231, and 30% to C. albicans ATCC 98028. Organic extracts of the HAA-16 and HAA-17 strands exhibited noticeable anti-Candida activity, being the ethyl acetate extract of the HAA-17 strand the one with the highest performance thanks to a wider activity spectrum of MIC 3.25 mg/mL against C. albicans ATCC 7516 and Candida parapsilosis ATCC 7307. The selected actinomyces were identified by means of molecular techniques as members of the Streptomyces genus. Conclusions. Actinomyces associated to Atta cephalotes are excellent producers of bioactive compounds, being able to inhibit the growth of pathogenic mold of the Candida genus and with potential for application in the development of new natural products for the biomedical field.

Dose-response effect of crude extracts produced by actinobacteria on in vitro rumen fermentation / Padrão dose-resposta de extratos brutos produzidos por actinobactérias sobre a fermentação ruminal in vitro

Actinobacteria have been researched as a source that produces crude extracts, which contain bioactive compounds able to act as antimicrobial agents. The present investigation evaluated the dose-response effect of two crude extracts, obtained at Caatinga rhizosphere (Caat) and Rhizophora mangle (AMC), on in vitro ruminal fermentation by:cumulative gas production, digestibility of dry (IVDMD) and organic matter (IVOMD), and short-chain fatty acids concentration (SCFA). Three multiparous Holstein dairy cows with ruminal fistula were used as the inoculum donors and fed a basal diet consisting of corn silage, soybean meal, urea, ground corn and mineral supplement. Ruminal fluid samples were incubated in glass bottles with 1 g of the dried and milled diet, a buffer solution, and the crude extracts evaluated in four doses (0.3, 0.6, 0.9 and 1.20 mg/10 mL inoculum) in a randomized block design, and the donators were considered as blocks with random effects. Additionally, negative controls were used. The results were expressed as average values based on triplicate analyses. Decreased cumulative gas production was observed according to linear dose response at 24, 48 and 72 h of incubation with the addition of Caat extract. The IVOMD showed a linear decrease at 72 h of incubation with dose Caat inclusion. Furthermore, the inclusion of Caat extract linearly reduced butyric and isovaleric acid concentrations, as well as acetate:propionate ratio. Finally, the Caat inclusion increased the propionic acid concentration in comparison to AMC extract. However, the inclusion of AMC extract did not affect any of the analyzed variables at the used doses. The Caat extract could be used as a modulator of in vitro ruminal fermentation, since it reduced acetate:propionate ratio and cumulative gas production.(AU)

As actinobactérias têm sido pesquisadas como fonte produtoras de extratos brutos que contêm compostos bioativos capazes de atuar como agentes antimicrobianos. O presente trabalho investigou o efeito dose-resposta de dois extratos brutos, AMC e Caat, na fermentação ruminal in vitro por: produção cumulativa de gás, digestibilidade in vitro da matéria seca (IVDMD) e matéria orgânica (IVOMD) e concentração de ácidos graxos de cadeia curta (SCFA). Três vacas leiteiras da raça Holandesa, multíparas e portadoras de fístula ruminal foram utilizadas como doadoras de inóculo ruminal e foram alimentadas com uma dieta basal composta por silagem de milho, farelo de soja, ureia, milho moído e suplemento mineral. As amostras de inóculo ruminal foram incubadas em garrafas de vidro com 1 g da dieta seca e moída, solução tampão e os extratos brutos avaliados em quatro doses (0,3, 0,6, 0,9 e 1,20 mg/10 mL de inóculo) em delineamento em blocos casualizados, sendo as doadoras consideradas os blocos como efeito aleatório. Além disso, foram utilizados controles negativos para a correção da produção de gás. Os resultados foram expressos como valores médios com base em análises triplicadas. A diminuição da produção cumulativa de gás foi observada de acordo com a dose em resposta linear às 24, 48 e 72 h de incubação com a adição de extrato de Caat. A IVOMD mostrou uma diminuição linear com 72 h de incubação com inclusão de Caat. Além disso, a inclusão do Caat reduziu linearmente as concentrações de ácido butírico e isovalérico, bem como a proporção de acetato/propionato. Diferentemente, a inclusão do extrato de AMC não afetou nenhuma das variáveis analisadas nas doses utilizadas. O extrato de Caat pode ser usado como um modulador da fermentação ruminal in vitro, uma vez que reduziu a proporção de acetato/propionato e a produção de gás acumulada. (AU)

Effect of sulfonylurea tribenuron methyl herbicide on soil Actinobacteria growth and characterization of resistant strains

ABSTRACT Repeated application of pesticides disturbs microbial communities and cause dysfunctions on soil biological processes. Granstar® 75 DF is one of the most used sulfonylurea herbicides on cereal crops; it contains 75% of tribenuron-methyl. Assessing the changes on soil microbiota, particularly on the most abundant bacterial groups, will be a useful approach to determine the impact of Granstar® herbicide. For this purpose, we analyzed Actinobacteria, which are known for their diversity, abundance, and aptitude to resist to xenobiotic substances. Using a selective medium for Actinobacteria, 42 strains were isolated from both untreated and Granstar® treated soils. The number of isolates recovered from the treated agricultural soil was fewer than that isolated from the corresponding untreated soil, suggesting a negative effect of Granstar® herbicide on Actinobacteria community. Even so, the number of strains isolated from untreated and treated forest soil was quite similar. Among the isolates, resistant strains, tolerating high doses of Granstar® ranging from 0.3 to 0.6% (v/v), were obtained. The two most resistant strains (SRK12 and SRK17) were isolated from treated soils showing the importance of prior exposure to herbicides for bacterial adaptation. SRK12 and SRK17 strains showed different morphological features. The phylogenetic analysis, based on 16S rRNA gene sequencing, clustered the SRK12 strain with four Streptomyces type strains (S. vinaceusdrappus, S. mutabilis, S. ghanaensis and S. enissocaesilis), while SRK17 strain was closely related to Streptomyces africanus. Both strains were unable to grow on tribenuron methyl as unique source of carbon, despite its advanced dissipation. On the other hand, when glucose was added to tribenuron methyl, the bacterial development was evident with even an improvement of the tribenuron methyl degradation. In all cases, as tribenuron methyl disappeared, two compounds were detected with increased concentrations. These by-products appeared to be persistent and were not degraded either chemically or by the studied strains. Based on these observations, we suggested that bacterial activity on carbon substrates could be directly involved in the partial breakdown of tribenuron methyl, by generating the required acidity for the first step of the hydrolysis. Such a process would be interesting to consider in bioremediation of neutral and alkaline tribenuron methyl-polluted soils.

Endophytic actinobacteria of medicinal plant Aloe vera: Isolation, antimicrobial, antioxidant, cytotoxicity assays and taxonomic study

Objective: To explore the new sources of novel bioactive compounds having pharmaceutical and agricultural interest and to search the endophytic actinobacteria from medicinal plants. Methods: NAF-1 an endophyte actinobacteria was isolated from leaves of medicinal plant Aloe vera collected in Marrakesh, Morocco using Bennett agar as selective medium. NAF-1 was tested for its antimicrobial activity against five pathogenic bacteria such as Staphylococcus aureus PIC 53156, Micrococcus luteus ATCC381, Bacillus subtilis ATCC 14579, Pseudomonas aeruginosa DSM 50090 and Escherichia coli ATCC 8739 and four human clinic fungi belonging to the Candida, Aspergillus and Microsporum genera. Several antioxidant activities were studied such as DPPH free radical scavenging, β -carotene and linoleic acid and reducing power assays. The total of phenol and flavonoid was also calculated. Using Artemia salina shrimp assay, the cytotoxicity of NAF-1 crude extract was determined. Results: The results revealed that the actinobacteria showed a high activity (≥20 mm) against only Gram positive bacteria but it had a moderate activity (between 13 and 15 mm) against Human clinic fungi. The isolate also exhibited a LD

Endophytic actinobacteria of medicinal plant Aloe vera: Isolation, antimicrobial, antioxidant, cytotoxicity assays and taxonomic study

Objective: To explore the new sources of novel bioactive compounds having pharmaceutical and agricultural interest and to search the endophytic actinobacteria from medicinal plants. Methods: NAF-1 an endophyte actinobacteria was isolated from leaves of medicinal plant Aloe vera collected in Marrakesh, Morocco using Bennett agar as selective medium. NAF-1 was tested for its antimicrobial activity against five pathogenic bacteria such asStaphylococcus aureus PIC 53156,Micrococcus luteus ATCC381,Bacillus subtilis ATCC 14579,Pseudomonas aeruginosa DSM 50090 and Escherichia coli ATCC 8739 and four human clinic fungi belonging to the Candida,Aspergillus and Microsporum genera. Several antioxidant activities were studied such as DPPH free radical scavenging,β-carotene and linoleic acid and reducing power assays. The total of phenol and flavonoid was also calculated. Using Artemia salina shrimp assay, the cytotoxicity of NAF-1 crude extract was determined.Results: The results revealed that the actinobacteria showed a high activity (≥20 mm) against only Gram positive bacteria but it had a moderate activity (between 13 and 15 mm) against Human clinic fungi. The isolate also exhibited a LD50 of 14.20 μg/mL in the cytotoxicity assay. The result showed that the crude extract presented an interesting free radical-scavenging activity with IC50 value of (5.58 ± 0.26) μg/mL and a high value of phenolic and flavonoid compounds with (15.41 ± 0.18) μg GAE/mg extract and (11.41± 0.06) μg QE/mg extract respectively. Moreover, the taxonomic position of our endophyte actinobacteria using the morphological and physiological criteria and using16SrRNA gene sequence (polyphasic approach) showed that the NAF-1 isolate was similar to Streptomyces hydrogenans which was never described as an endophyte actinobacteria. Conclusions: This isolated strain appears promising resources of bioactive agents and can be exploited to produce therapeutic agents active against pathogenic disease.