Respiration in Azotobacter vinelandii and its relationship with the synthesis of biopolymers

Azotobacter vinelandii is a gram-negative soil bacterium that produces two biopolymers of biotechnological interest, alginate and poly(3-hydroxybutyrate), and it has been widely studied because of its capability to fix nitrogen even in the presence of oxygen. This bacterium is characterized by its high respiration rates, which are almost 10-fold higher than those of Escherichia coli and are a disadvantage for fermentation processes. On the other hand, several works have demonstrated that adequate control of the oxygen supply in A. vinelandii cultivations determines the yields and physicochemical characteristics of alginate and poly(3-hydroxybutyrate). Here, we summarize a review of the characteristics of A. vinelandii related to its respiration systems, as well as some of the most important findings on the oxygen consumption rates as a function of the cultivation parameters and biopolymer production.

Vitamina D na modulação da microbiota intestinal: associações com os perfis inflamatório e cardiometabólico / Vitamin D in intestinal microbiota modulation: associations with inflammatory and cardiometabolic profiles

Introdução: Bactérias intestinais influenciam a resposta imune e conhecendo-se as ações imunomoduladoras da vitamina D passou-se a investigar sua relação com a microbiota. O status adequado desta vitamina está associado a uma composição mais saudável da microbiota, enquanto sua deficiência pode acarretar disbiose intestinal, endotoxemia, inflamação e resistência à insulina. O conhecimento de interações do status de vitamina D com a microbiota pode melhorar a compreensão da gênese de doenças crônicas mediadas pela inflamação. Objetivo: Examinou-se a associação da ingestão e concentração de vitamina D com a composição da microbiota fecal, marcadores inflamatórios e perfil bioquímico de participantes do Nutritionists Health Study. Métodos: Nesta análise transversal, 150 adultos jovens foram estratificados em tercis de consumo e de concentração de 25(OH)D e comparados quanto ao perfil clínico e inflamatório. A associação de 25(OH)D com a microbiota (sequenciamento do 16S rRNA, região V4, Illumina® MiSeq) foi testada por regressão linear múltipla. Resultados: A ingestão de vitamina D se associou aos níveis séricos (p < 0,05). Não foram observadas diferenças significantes de variáveis clínicas e inflamatórias entre os tercis de ingestão, exceto tendência de aumento do LPS com a redução da 25(OH)D (p-trend < 0,05). Prevotella foi mais abundante (log2FC 1,67; p < 0,01), e Haemophilus and Veillonella menos abundantes (log2FC -2,92 e -1,46; p < 0,01, respectivamente) no subgrupo com maior ingestão de vitamina D (referência) comparado aos outros grupos (primeiro e segundo tercis). PCR (r = -0,170; p = 0,039), selectina-E (r = -0,220; p = 0,007) e abundância de Coprococcus (r = -0,215; p = 0,008) e de Bifdobacterium (r = -0,269; p = 0,001) foram inversamente correlacionados com 25(OH)D. Após ajustes por idade, sexo, estação do ano e IMC, a 25(OH)D manteve associação inversa com Coprococcus ( = -9,414; p = 0,045) e Bifdobacterium ( = -1,881; p = 0,051), mas a significância desapareceu com a adição de marcadores inflamatórios aos modelos. Conclusão: Associações de ingestão e concentração de vitamina D com abundância de certos gêneros da microbiota sugerem que sua ação imunomoduladora poderia influenciar a composição bacteriana. Abundância relativamente maior de gram-negativos (Haemophilus e Veillonella) pode ter sido facilitada pela baixa ingestão e/ou concentração da vitamina. Menor proporção de bactérias benéficas (Coprococcus e Bifidobacterium) poderia estimular a resposta imune e inflamação. Concluímos que a participação da vitamina D na manutenção da homeostase imune deve ocorrer em parte pelas interações com a microbiota intestinal, embora o delineamento transversal impeça assegurar relações tipo causa-efeito

Introduction: Gut bacteria influence the immune response and due the immunomodulatory actions of vitamin D, it has been investigated its relationship with the microbiota. Adequate status of this vitamin is associated with adequate composition of the microbiota, while its deficiency can cause gut dysbiosis, endotoxemia, inflammation and insulin resistance. The knowledge of interactions of vitamin D status with the microbiota may improve the understanding of the genesis of inflammation-mediated chronic diseases. Objective: We examined the association of vitamin D intake and concentration with the composition of fecal microbiota, inflammatory markers and biochemical profile of participants from the Nutritionists' Health Study. Methods: In this cross-sectional analysis, 150 healthy young adults were stratified into tertiles of intake and concentrations of vitamin D and their clinical and inflammatory profiles were compared. The association between 25(OH)D and fecal microbiota (16S rRNA sequencing, V4 region, Illumina® MiSeq) was tested by multiple linear regression.) Results: Vitamin D intake was associated with its concentration (p<0.05). There were no significant differences in clinical and inflammatory variables across tertiles of intake, except for a trend of LPS increases with reduction of 25(OH)D (p-trend <0.05). Prevotella was more abundant (log2FC 1.67; p <0.01), and Haemophilus and Veillonella less abundant (log2FC -2,92 e -1.46; p <0.01, respectively) in subset with the highest vitamin D intake (reference) than that observed in the other subset (first plus second tertiles). CRP (r=-0.170, p=0.039), E-selectin (r=-0.220, p=0.007) and abundances of Coprococcus (r=-0.215, p=0.008) and Bifdobacterium (r=-0.269, p=0.001) were inversely correlated with 25(OH)D. After adjusting for age, sex, season and BMI, the 25(OH)D maintained inversely associated with Coprococcus (=-9.414, p=0.045) and Bifdobacterium (=-1.881, p=0.051), but significance disappeared following the addition of inflammatory markers in the regression models. Conclusion: Association of vitamin D intake and concentration with abundance of certain genera of microbiota suggests that its immunomodulatory action could influence the bacterial composition. Relatively higher abundance of gram-negative (Haemophilus and Veillonella) may have been facilitated by the low intake and/or concentration of the vitamin. Lower proportion of beneficial bacteria (Coprococcus and Bifidobacterium) could stimulate the immune response and inflammation. We conclude that the role of vitamin D in maintaining immune homeostasis should occur in part by interactions with the gut microbiota, although the cross-sectional design does not allow ensuring cause-effect relationships

Evaluation of different detection methods of biofilm formation in the clinical isolates

BACKGROUND: Microorganisms growing in a biofilm are associated with chronic and recurrent human infections and are highly resistant to antimicrobial agents. There are various methods to detect biofilm production like Tissue Culture Plate (TCP), Tube method (TM), Congo Red Agar method (CRA), bioluminescent assay, piezoelectric sensors, and fluorescent microscopic examination. OBJECTIVE: This study was conducted to compare three methods for the detection of biofilms. METHOD: The study was carried out at the Department of Microbiology, Army Medical College, National University of Sciences and Technology, Pakistan, from January 2010 to June 2010. A total of 110 clinical isolates were subjected to biofilm detection methods. Isolates were identified by standard microbiological procedures. Biofilm detection was tested by TCP, TM and CRA. Antibiotic susceptibility test of biofilm producing bacteria was performed by using the Kirby-Bauer disc diffusion technique according to CLSI guidelines. RESULTS: The TCP method was considered to be superior to TM and CRA. From the total of 110 clinical isolates, TCP method detected 22.7 percent as high, 41 percent moderate and 36.3 percent as weak or non-biofilm producers. We have observed higher antibiotic resistance in biofilm producing bacteria than non-biofilm producers. CONCLUSION: We can conclude from our study that the TCP method is a more quantitative and reliable method for the detection of biofilm forming microorganisms as compared to TM and CRA methods, and it can be recommended as a general screening method for detection of biofilm producing bacteria in laboratories.

Clinical status and detection of periodontopathogens and Streptococcus mutans in children with high levels of supragingival biofilm

Knowledge about the presence of some important oral pathogens is an important step in better identifying children at risk for periodontal and/or caries diseases in later life. The purpose of this study was to detect the presence of Streptococcus mutans (Sm), Aggregatibacter actinomycetemcomitans (Aa), Campylobacter rectus (Cr), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), and Tannerella forsythia (Tf) in gingival biofilm samples from 196 children, and to assess whether any of these pathogens are more associated with gingival inflammation extension and the Decayed/Missing/Filled teeth (DMFT/dmft) index. The subjects presented plaque index greater than 80 percent and were divided in 3 groups according to the bleeding index (BI): I) Low bleeding (< 30 percent), II) Medium bleeding (31 - 59 percent) and III) High bleeding (> 60 percent). The presence of each pathogen was determined by PCR. The prevalence of Sm was 71.9 percent and the mean dmft/DMFT was 6.68. The prevalence in low, medium and high bleeding groups was 43.5 percent, 34.5 percent and 46.7 percent for Aa; 43.5 percent, 37.9 percent, and 36.7 percent for Cr; 99.1 percent, 100 percent, and 96.7 percent for Pg; 56.5 percent, 56.9 percent, and 66.7 percent for Pi; and 58.3 percent, 60.3 percent, and 56.7 percent for Tf, respectively. Pg (99.0 percent) was the most prevalent periodontal pathogen detected followed by Tf (58.7 percent), Pi (58.2 percent), Aa (41.3 percent) and Cr (40.8 percent). Our study indicated that in this high plaque index population studied, a high prevalence of Sm and high mean DMFT were observed. In addition, the presence of Pi was associated with the presence of inflammation (P < 0.05) whereas Cr was associated with periodontal health (P < 0.05).

Survival and surface adherence ability of bacterial pathogens in oral liquid pharmaceuticals and their containers

The survival and surface adherence ability of Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa in nutrient broth and in five oral liquid pharmaceuticals (nivaquine syrup, cough mixture, paracetamol elixir, cotrimoxazole and vitamin C) were investigated The bacteria grew more in nutrient broth than in the pharmaceuticals (p < 0. 001) and the recovery of stressed cells was enhanced when 3 Tween 80 was used as the recovery medium as against the use of normal saline (p < 0.01). The Gram-negative bacteria were more adapted to the pharmaceuticals than their Gram-positive counterparts. Klebsiella pneumoniae and Ps. aeruginosa were recovered in large numbers from nivaquine and cotrimoxazole suspensions that did not support the growth of the other bacteria. The effect of bacterial growth on the physico-chemical properties of the pharmaceuticals was also evaluated The properties were not altered significantly except for pH shifts of 0.3 to 1.1 caused by E. coli and S. aureus in paracetamol and vitamin C. Adherence capability was found to correlate with the survival ability of the bacteria. Populations on coupons were significantly higher when nutrient broth was used as the suspending medium compared with any of the pharmaceuticals (p < 0.01). Rubber and plastic coupons were significantly more accessible to the bacteria than glass coupon as revealed by the high population of bacteria recovered from their surfaces

Termorresistência de bactéria psicrotrófica produtora de ácido isolada de leite / Thermo resistance of acid producing psychrotrophic bacteria isolated from milk

Bactéria psicotrófica acidificante foi isolada de leite cru, em meio Agar Púrpura de Bromocresol, após incubação a 7 grados Celsius por 10 dias. Células da cultura, no início da fase estacionária, foram inoculadas em leite em pó, reconstituído a 12 por ciento de sólidos totais e esterelizados, resultando em, aproximadamente, 10(8) células por mililitro. Porções de 3 ml do leite inoculado foram transferidas para tubos de borossilicato e submetidos à determinação da resistência das células a 62, 70, 75 e 80 grados Celsius, pelo método do TDT tubo. As curvas de sobrevivência nas respectivas temperaturas e a curva de morte térmica foram traçadas. A bactéria apresentou um valor de D75 grados Celsius de 0,15 minutos e z igual a 8,7 grados Celsius. A pasteurização pelos sistemas LTLT e HTST promoveram, respectivamente, 5,27 e 0,53 reduções decimais no número de células viáveis da bactéria. Conclui-se que a bactéria isolada neste estudo é destruída apenas pela pasteurização pelo sistema LTLT.

Comportamiento de cultivos mixtos bacterianos que utilizan metanol para biosíntesis de proteinas / Growth behavior of mixed bacterial cultures on methanol

Utilizando metanol como única fuente de carbono y energía, se aislaron diez cultivos mixtos, constituidos al menos por dos tipos de bacterias, morfológicamente diferentes. Las bacterias son Gram negativas y tienen como forma predominante la bacilar. Difieren en la apariencia de sus colonias, principalmente en el tamaño y grado de viscosidad. La colonias en medio sintético son apigmenteadas y cuando desarrollan en medios complejos son de color amarillo cremoso. Las bacterias que integran los cultivos mixtos no desarrollaron por separado en medio mineral, pero sí en un medio complejo, lo cual indica que se trata de metilótrofos facultativo. Dos de los cultivos (CM-3 y CM-15) fueron seleccionados para llevar a efecto estudios de producción de biomasa en fermentadores. Un tercer cultivo (CM-3A) que fue aislado a partir del CM-3 en cultivo continuo, fue tambiém seleccinado para el mismo propósito. En un sistema intermitente se establecieron las condiciones óptimas para el crecimiento (temperatura 37-C, concentración de metanol de 1.5% (v/v) y pH de 6.9 a 7.0). Los valores de las velocidades específicas de crecimiento fueron de 0.46 h-1 a 0.50 h-1 con tiempos de generación entr 1.50 h y 1.38 h. En cultivo continuo, los cultivos mixtos presentaron oscilaciones amplias sin haverse logrado estabilizar a ninguna de las velocidades de dilución ensayadas. Debido a estas oscilaciones se incluyeron valores promedio de concentración celular y de productividad. En general fueron poco susceptibles a la contaminación. Los cultivos CM-15 y CM-3 sintetizaron una substancia mucoide cuya concentración fue dependiente de las condiciones de operación. La velocidad específica de crecimiento máxima, determinada en sistema continuo, fue menor que la determinada en sistema intermitentee