The different effects of molybdate on Hg(II) bio-methylation in aerobic and anaerobic bacteria.

In nature, methylmercury (MeHg) is primarily generated through microbial metabolism, and the ability of bacteria to methylate Hg(II) depends on both bacterial properties and environmental factors. It is widely known that, as a metabolic analog, molybdate can inhibit the sulfate reduction process and affect the growth and methylation of sulfate-reducing bacteria (SRB). However, after it enters the cell, molybdate can be involved in various intracellular metabolic pathways as a molybdenum cofactor; whether fluctuations in its concentration affect the growth and methylation of aerobic mercury methylating strains remains unknown. To address this gap, aerobic γ-Proteobacteria strains Raoultella terrigena TGRB3 (B3) and Pseudomonas putida TGRB4 (B4), as well as an obligate anaerobic δ-Proteobacteria strain of the SRB Desulfomicrobium escambiense CGMCC 1.3481 (DE), were used as experimental strains. The growth and methylation ability of each strain were analyzed under conditions of 500 ng·L-1 Hg(II), 0 and 21% of oxygen, and 0, 0.25, 0.50, and 1 mM of MoO4 2-. In addition, in order to explore the metabolic specificity of aerobic strains, transcriptomic data of the facultative mercury-methylated strain B3 were further analyzed in an aerobic mercuric environment. The results indicated that: (a) molybdate significantly inhibited the growth of DE, while B3 and B4 exhibited normal growth. (b) Under anaerobic conditions, in DE, the MeHg content decreased significantly with increasing molybdate concentration, while in B3, MeHg production was unaffected. Furthermore, under aerobic conditions, the MeHg productions of B3 and B4 were not influenced by the molybdate concentration. (c) The transcriptomic analysis showed several genes that were annotated as members of the molybdenum oxidoreductase family of B3 and that exhibited significant differential expression. These findings suggest that the differential expression of molybdenum-binding proteins might be related to their involvement in energy metabolism pathways that utilize nitrate and dimethyl sulfoxide as electron acceptors. Aerobic bacteria, such as B3 and B4, might possess distinct Hg(II) biotransformation pathways from anaerobic SRB, rendering their growth and biomethylation abilities unaffected by molybdate.

Effect of micro-aeration on syntrophic and methanogenic activity in anaerobic sludge.

Micro-aeration was shown to improve anaerobic digestion (AD) processes, although oxygen is known to inhibit obligate anaerobes, such as syntrophic communities of bacteria and methanogens. The effect of micro-aeration on the activity and microbial interaction in syntrophic communities, as well as on the potential establishment of synergetic relationships with facultative anaerobic bacteria (FAB) or aerobic bacteria (AB), was investigated. Anaerobic sludge was incubated with ethanol and increasing oxygen concentrations (0-5% in the headspace). Assays with acetate or H2/CO2 (direct substrates for methanogens) were also performed. When compared with the controls (0% O2), oxygen significantly decreased substrate consumption and initial methane production rate (MPR) from acetate or H2/CO2. At 0.5% O2, MPR from these substrates was inhibited 30-40%, and close to 100% at 5% O2. With ethanol, significant inhibition (>36%) was only observed for oxygen concentrations higher than 2.5%. Oxygen was consumed in the assays, pointing to the stimulation of AB/FAB by ethanol, which helped to protect the syntrophic consortia under micro-aerobic conditions. This highlights the importance of AB/FAB in maintaining functional and resilient syntrophic communities, which is relevant for real AD systems (in which vestigial O2 amounts are frequently present), as well as for AD systems using micro-aeration as a process strategy. KEY POINTS: •Micro-aeration impacts syntrophic communities of bacteria and methanogens. •Oxygen stimulates AB/FAB, maintaining functional and resilient consortia. •Micro-aeration studies are critical for systems using micro-aeration as a process strategy.

The Isolation of Anaerobic and Facultative Anaerobic Sulfate-Reducing Bacteria (SRB) and a Comparison of Related Enzymes in Their Sulfate Reduction Pathways.

Sulfate-reducing bacteria (SRB) are an important group of microorganisms that cause microbial corrosion. In this study, culturable SRB were isolated and identified from the inner rust layer of three kinds of steel and from sediments, and a comparison of amino acid sequences encoding related enzymes in the sulfate reduction pathway between anaerobic and facultative anaerobic SRB strains was carried out. The main results are as follows. (1) Seventy-seven strains were isolated, belonging to five genera and seven species, with the majority being Desulfovibrio marinisediminis. For the first time, Holodesulfovibrio spirochaetisodalis and Acinetobacter bereziniae were separated from the inner rust layer of metal, and sulfate reduction by A. bereziniae, Virgibacillus dokdonensis, and Virgibacillus chiguensis, etc., was also demonstrated for the first time. (2) Three strains of strictly anaerobic bacteria and four strains of facultative anaerobic bacteria were screened from seven bacterial strains. (3) Most of the anaerobic SRB only contained enzymes for the dissimilatory sulfate reduction pathway, while those of facultative anaerobic bacteria capable of producing hydrogen sulfide included two possible ways: containing the related enzymes from the dissimilatory pathway only, or containing enzymes from both dissimilatory and assimilation pathways. This study newly discovered that some bacterial genera exhibit sulfate reduction ability and found that there are differences in the distribution of enzymes related to the sulfate reduction pathway between anaerobic and facultative anaerobic SRB type trains, providing a basis for the development and utilization of sulfate-reducing bacterial resources and furthering our understanding of the metabolic mechanisms of SRB.

Aerobic and facultative anaerobic Klebsiella pneumoniae strains establish mutual competition and jointly promote Musca domestica development.

Introduction: The gut microenvironment in housefly harbors a rich and diverse microbial community which plays a crucial role in larval development. However, little is known about the impact of specific symbiotic bacteria on larval development as well as the composition of the indigenous gut microbiota of housefly. Methods: In the present study, two novel strains were isolated from housefly larval gut, i.e., Klebsiella pneumoniae KX (aerobe) and K. pneumoniae KY (facultative anaerobe). Moreover, the bacteriophages KXP/KYP specific for strains KX and KY were used to analyse the effects of K. pneumoniae on larval development. Results: Our results showed that dietary supplementation with K. pneumoniae KX and KY individually promoted housefly larval growth. However, no significant synergistic effect was observed when the two bacterial strains were administered in combination. In addition, using high-throughput sequencing, it was demonstrated that the abundance of Klebsiella increased whereas that of Provincia, Serratia and Morganella decreased when housefly larvae received supplementation with K. pneumoniae KX, KY or the KX-KY mixture. Moreover, when used combined, K. pneumoniae KX/KY inhibited the growth of Pseudomonas and Providencia. When the abundance of both bacterial strains simultaneously increased, a balance in total bacterial abundance was reached. Discussion: Thus, it can be assumed that strains K. pneumoniae KX and KY maintain an equilibrium to facilitate their development in housefly gut, by establishing competition but also cooperation with each other to maintain the constant composition of gut bacteria in housefly larvae. Thus, our findings highlight the essential role of K. pneumoniae in regulating the composition of the gut microbiota in insects.

Growth of various obligate and facultative anaerobic intestinal bacteria in cell culture medium under aerobic and anaerobic culture conditions.

Eight bacterial strains were used in this study to examine the survival of intestinal bacteria in immune cell cultures under aerobic and anaerobic culture conditions. With the addition of penicillin G and streptomycin, viable Clostridium clostridioforme and Fusobacterium varium cells did not decrease after 6 or 24 hr, even under aerobic conditions. Without antibiotics, eight bacterial strains did not decrease until 4 or 6 hr later, under both aerobic and anaerobic conditions. Escherichia coli numbers increased by more than 10 times under both conditions. In order to examine the effects of live gut bacteria on various immune cells, the viability of bacteria should be checked in cell culture media and under different conditions.

Emphysematous pyelonephritis: Six case reports and review of literature.

BACKGROUND: Emphysematous pyelonephritis (EPN) is a severe acute necrotizing infection of the renal parenchyma and surrounding tissues that causes the presence of gas in the renal parenchyma, collecting system, or perinephric tissue and has a poor prognosis. EPN occurs primarily in people with diabetes mellitus (DM), but can occur in those without DM when the associated renoureteral unit is obstructed. CASE SUMMARY: We describe our experience with six patients who developed EPN. Five patients had DM, including one with diabetic ketoacidosis, one with multisystem involvements, including eye, lung and brain. Bilateral urolithiasis was present in one case, along with emphysematous cystitis. Unilateral kidney stones were present in one patient. One patient was an older man in poor general health. Five individuals survived and underwent surgical procedures including ureteral stent installation (Double J stent placement), percutaneous nephrostomy and perinephric abscess puncture drainage, while one died because the patient's family chose to terminate therapy. Klebsiella pneumoniae and Escherichia coli were the microorganisms implicated. CONCLUSION: We conclude that EPN is a potentially fatal illness. A positive outcome necessitates early detection. Therapeutic measures should be implemented as soon as a diagnosis is made.

Characterization of a thermophilic facultatively anaerobic bacterium Paenibacillus sp. strain DA-C8 that exhibits xylan degradation under anaerobic conditions.

The screening, identification, and study of the functional properties of cellulolytic xylanolytic bacteria are crucial for the construction of applicable bioprocesses. The thermophilic facultatively anaerobic, xylanolytic bacterial strain DA-C8 (=JCM34211=DSM111723) exhibiting efficient xylan degradation was newly isolated from compost. Strain DA-C8 completely degraded 1% beechwood xylan within 4 days under anaerobic conditions. By 16S rRNA gene sequence homology and phylogenetic tree analysis, strain DA-C8 was closely related to Paenibacillus cisolokensis and Xylanibacillus composti; however, the average nucleotide identity and digital DNA-DNA hybridization values based on genome information and the carbon source utilization properties indicated that strain DA-C8 belongs to Paenibacillus rather than Xylanibacillus. The gene numbers of xylanase and endoglucanase of strain DA-C8 and X. composti were not different; however, strain DA-C8 had higher abundance of α-L-arabinofuranosidase, ß-xylosidase, and ß-glucosidase than X. composti. Strain DA-C8 showed decreased xylan and corn hull degradation abilities and growth on xylan medium under aerobic conditions. Quantitative PCR showed high expression of xylan and cellulose degradation genes under anaerobic conditions, but the genes were repressed under aerobic conditions, indicating that strain DA-C8 controls polysaccharide degradation depending on the aeration conditions. Strain DA-C8 is a new species of Paenibacillus with a unique polysaccharide degradation system.

Selective Adsorption of Amino Acids in Crystals of Monohydrocalcite Induced by the Facultative Anaerobic Enterobacter ludwigii SYB1.

The morphology, crystal structure, and elemental composition of biominerals are commonly different from chemically synthesized minerals, but the reasons for these are not fully understood. A facultative anaerobic bacterium, Enterobacter ludwigii SYB1, is used in experiments to document the hydrochemistry, mineral crystallization, and cell surface characteristics of biomineralization. It was found that carbonate anhydrase and ammonia production were major factors influencing the alkalinity and saturation of the closed biosystem. X-ray diffraction (XRD) spectra showed that calcite, monohydrocalcite (MHC), and dypingite formed in samples with bacterial cells. It was also found that the (222) plane of MHC was the preferred orientation compared to standard data. Scanning transmission electron microscopy (STEM) analysis of cell slices provides direct evidence of concentrated calcium and magnesium ions on the surface of extracellular polymeric substances (EPS). In addition, high-resolution transmission electron microscopy (HRTEM) showed that crystallized nanoparticles were formed within the EPS. Thus, the mechanism of the biomineralization induced by E. ludwigii SYB1 can be divided into three stages: (i) the production of carbonate anhydrase and ammonia increases the alkalinity and saturation state of the milieu, (ii) free calcium and magnesium ions are adsorbed and chelated onto EPS, and (iii) nanominerals crystallize and grow within the EPS. Seventeen kinds of amino acids were identified within both biotic MHC and the EPS of SYB1, while the percentages of glutamic and aspartic acid in MHC increased significantly (p < 0.05). Furthermore, the adsorption energy was calculated for various amino acids on seven diffracted crystal faces, with preferential adsorption demonstrated on (111) and (222) faces. At the same time, the lowest adsorption energy was always that of glutamic and aspartic acid for the same crystal plane. These results suggest that aspartic and glutamic acid always mix preferentially in the crystal lattice of MHC and that differential adsorption of amino acids on crystal planes can lead to their preferred orientation. Moreover, the mixing of amino acids in the mineral structure may also have a certain influence on the mineral lattice dislocations, thus enhancing the thermodynamic characteristics.

The efficiencies of inorganic mercury bio-methylation by aerobic bacteria under different oxygen concentrations.

Limited information is available about the bio-methylation of inorganic mercury (iHg) under aerobic conditions. In this study, two γ-proteobacteria strains (P. fluorescens TGR-B2 and P. putida TGR-B4) were obtained from the soil of The Three Gorges Reservoir (TGR), demonstrating effective aerobic transformation capacities of iHg into methylmercury (MeHg). Based on periodical changes in soil oxygen content of the TGR, a culture system was established, in which 300 ng Hg (II) L-1 and O2 were set at 7%, 14%, and 21%, respectively. Results indicated that the two strains differed significantly in bacterial growth rate and MeHg production. The kinetic model of MeHg showed typical characteristics of a "two-staged" process: The first stage was dominated by bio-methylation, which was shown by increasing of net MeHg content. Moreover, the second stage was dominated by bio-demethylation, which decreased net MeHg content. Thus, we hypothesized that the mechanism of aerobic bacterial iHg bio-methylation: (1) should inefficiency compared to anaerobic bacteria i.e.SRB, which were regulated by hgcA/B gene clusters, (2) might be regarded as a passive stress response and depended on the bacterial iHg intoxication threshold and MeHg tolerance threshold.

Effective degradation of polychlorinated biphenyls by a facultative anaerobic bacterial consortium using alternating anaerobic aerobic treatments.

Polychlorinated biphenyls (PCBs) are synthetic mixtures of chlorinated hydrocarbon compounds that were widely used in the past and still found in the environment due to their highly recalcitrant nature. A combination of anaerobic dechlorination and aerobic oxidation is essential to degrade these PCB mixtures into less toxic products. It was hypothesized that due to the complexity of PCB mixtures, a consortium of carefully selected suitable microbial species will perform better than the application of individual microbes. In the present study, biodegradation of the commercial PCB mixture, Aroclor 1260, was studied under two different combined anaerobic-aerobic conditions, namely, alternating (AN) and two stage (TS). The facultative anaerobic bacterial consortium consisted of naturally occurring Achromobacter sp. NP03, Ochrobactrum sp. NP04 and Lysinibacillus sp. NP05. These bacteria were found capable as individuals of solubilizing and degrading PCBs under both anaerobic and aerobic conditions. 49.2 ±â€¯2.5% total reduction of the original 50 mg/L Aroclor 1260 mixture was achieved after 2 weeks in AN treatment whereas the reduction was only 24.44 ±â€¯2.46% in TS treatment. At the end of week 6, a yield of 17.63 ±â€¯0.91 mg/L chloride released was measured under AN condition compared to 11.79 ±â€¯1.28 mg/L measured under TS condition. The overall results suggested that the microbial consortia capable of degrading and utilizing PCBs under both, anaerobic and aerobic conditions achieved better PCB degradation by repeated exposure to short periods of anaerobic and aerobic conditions alternatingly rather than the conventional two stage anaerobic-aerobic conditions.

Microbial ecology of fermentative hydrogen producing bioprocesses: useful insights for driving the ecosystem function.

One of the most important biotechnological challenges is to develop environment friendly technologies to produce new sources of energy. Microbial production of biohydrogen through dark fermentation, by conversion of residual biomass, is an attractive solution for short-term development of bioH2 producing processes. Efficient biohydrogen production relies on complex mixed communities working in tight interaction. Species composition and functional traits are of crucial importance to maintain the ecosystem service. The analysis of microbial community revealed a wide phylogenetic diversity that contributes in different-and still mostly unclear-ways to hydrogen production. Bridging this gap of knowledge between microbial ecology features and ecosystem functionality is essential to optimize the bioprocess and develop strategies toward a maximization of the efficiency and stability of substrate conversion. The aim of this review is to provide a comprehensive overview of the most up-to-date biodata available and discuss the main microbial community features of biohydrogen engineered ecosystems, with a special emphasis on the crucial role of interactions and the relationships between species composition and ecosystem service. The elucidation of intricate relationships between community structure and ecosystem function would make possible to drive ecosystems toward an improved functionality on the basis of microbial ecology principles.

The evaluation of cultivable microbiota profile in patients with secondary endodontic infection before and after photo-activated disinfection.

BACKGROUND: Secondary/persistent endodontic infection can be the outcome of failure of endodontic treatment. Photo-activated disinfection (PAD) can be a useful adjunct to mechanical and antimicrobial agents in eliminating endopathogenic microorganisms. In this study, we evaluated the effect of PAD on diversity and count of microbiota related to secondary/persistent endodontic infections. MATERIALS AND METHODS: Root canal samples were taken using sterile paper points from the root canals of 14 patients with secondary/persistent endodontic infections after removing the root-canal filling materials. PAD was performed on teeth with toluidine blue O (TBO) in combination with diode laser. Then re-sampling was conducted from the canal root using sterile paper points and transferred to transport medium. The samples were plated and pure cultures of the target microorganisms were then isolated and identified by analytical profile index (API ® 20A) assays and 16S ribosomal RNA gene sequencing. RESULTS: Before TBO-PAD, a total of 31 cultivable isolates could be retrieved; 25.8% of the isolated species were obligate anaerobic or microphilics including Veillonella parvula, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Propionibacterium acnes, and Lactobacillus acidophilus, and 74.2% of the isolated species were facultative anaerobic such as Enterococcus faecalis, Actinomyces naeslundii, L. rhamnosus, L. casei, Streptococcus sanguinis, S. mitis, and Candida albicans. According to this in vivo study, the diversity and count of microbiota in root canal-treated teeth were decreased after TBO-PAD, so that E. faecalis, V. parvula, and C. albicans were the microorganisms that recovered after PAD. CONCLUSION: TBO-PAD is an effective approach that exhibited anti-microbial potential activity against microbiota involved in secondary/persistent endodontic infection.

Culture-dependent approaches to explore the prevalence of root canal pathogens from endodontic infections

Abstract: Endodontic infections are considered to be caused by the presence of various microorganisms within the root canal system. Recognition of this microbiota contributes to the successful treatment of infected root canals. This study investigated the microorganisms associated with primary and secondary endodontic infections via culture methods, biochemical tests, and molecular approaches in an Iranian population. Microbial specimens were collected from 36 patients with primary endodontic infection and 14 patients with a history of root canal therapy. Advanced microbiological culture techniques were used to isolate microbiota; subsequently, biochemical tests and 16S ribosomal RNA gene sequencing were performed to identify the microorganisms. Within the total 218 cultivable isolates, Veillonella parvula (20.6%) was found to occur with the highest frequency in primary endodontic infection, followed by Porphyromonas gingivalis (14.1%), and Aggregatibacter actinomycetemcomitans (9.2%). Enterococcus faecalis (36.6%) was the most predominant microorganism in secondary endodontic infections, followed by Candida albicans, Propionibacterium acnes, and V. parvula with frequencies of 20%, 2%, and 2%, respectively. It was concluded that V. parvula and E. faecalis was most frequently found in primary and secondary endodontic infections, respectively.

Considerações sobre 5.360 hemoculturas realizadas no Instituto Adolfo Lutz, São Paulo / 5,360 blood cultures carried out in Instituto Adolfo Lutz, Sao Paulo

Foram analisados os resultados de 5.360 culturas de sangue de pacientes provenientes do Hospital de Isolamento "Emílio Ribas", Hospital Infantil Cândido Fontoura, e do Instituto da Criança do Hospital das Clínicas, no município de São Paulo, SP, durante o período de 1978 a 1982, em relação à incidência de infecções bacterianas mistas, faixas etárias, e à resistência das cepas isoladas aos antibióticos e sulfonamidas. As hemoculturas foram positivas em 19,70% dos casos, sendo que 18,060/0 correspondeu a infecções simples, enquanto que em 1,64% dos casos positivos foi encontrado mais de um germe como agente etiológico. Nas infecções simples evidenciou-se a predominância da Salrnonella typhirnuriurn em 24,40% dos casos, seguida pelo Staphylococcus aureus e Salrnonella typhi, com 17,67 e 11,15%, respectivamente. Nas infecções mistas houve a predominância da Klebsiella pneurnoniae em 20,91% dos casos, seguida pela S. typhirnuriurn e Eechcrichia coli em 18,38 e 14,28% respectivamente, associadas entre si ou com outras bactérias. Foi digno de nota que em 7 casos foram isoladas cepas de Shiçeilo. fleteneri pertencentes aos sorotipos 2 (4 casos), 3 (2 casos) e 4 (1 caso). Com relação à sensibilidade aos antibióticos testados, observou-se grande resistência da S. typhirnuriurn, P. aeriujinoso. e K. pneurnoniae a vários destes antibióticos. As cepas de S. typhirnuriurn apresentaram 100% de sensibilidade ao c1oranfenicol (AU).