Cocos gram-positivos anaeróbios estritos da cavidade oral e do trato intestinal de primatas Calitriquídeos (Callithrix jacchus e Callithrix penicillata) mantidos em cativeiro.

<span class="texto">Este trabalho descreve a recuperação e a identificação de cocos gram-positivos anaeróbios estritos da cavidade oral e em espécimes fecais de sagüis Calitriquídeos, mantidos em cativeiro no Centro de Bioterismo do Instituto de Ciências Biológicas/UFMG. Foram coletados espécimes fecais e orais de oito animais, cultivados em ágar sangue com neomicina e em caldo tioglicolato suplementado. As cepas isoladas foram identificadas segundo as suas características morfocoloniais, morfotintoriais, respiratórias e testes bioquímicos. Foram recuperados cocos gram-positivos anaeróbios em espécimes orais e fecais, observando-se maior recuperação na cavidade oral. De espécimes orais foram isolados Streptococcus intermedius, Peptostreptococcus prevotii, Streptococcus parvulus, e Streptococcus sp. aerotolerante. Nos espécimes fecais, foram isolados Peptostreptococcus sp., Peptostreptococcus productus e Streptococcus parvulus. Os resultados obtidos representam contribuição original para o conhecimento da microbiota oral e intestinal de Calitriquídeos, tendo significado para a Microbiologia comparada, por estar o grupo microbiano em estudo entre os anaeróbios mais freqüentes em infecções humanas.</span>

Differential Induction of Colitis and Gastritis in HLA-B27 Transgenic Rats Selectively Colonized with Bacteroides vulgatus or Escherichia coli

ABSTRACT Resident bacteria play an important role in initiating and perpetuating gastrointestinal inflammation. We previously demonstrated that six commensal bacteria including Bacteroides vulgatuscaused more aggressive colitis and gastritis in HLA-B27 transgenic rats than did the other five bacteria without B. vulgatus. This study compared the degree of gastrointestinal inflammation in gnotobiotic HLA-B27 transgenic rats monoassociated with either B. vulgatus or Escherichia coli. Gnotobiotic transgenic rats raised in Trexler isolators were selectively colonized with eitherB. vulgatus or E. coli. Control rats were either germfree or colonized with six common commensal bacteria (Streptococcus faecium, E. coli,Streptococcus avium, Eubacterium contortum,Peptostreptococcus productus, and B. vulgatus[DESEP-B]). After 1 month, all the rats were killed and tissues were prepared for histologic and biochemical evaluation. Colitis induced byB. vulgatus monoassociation was almost equal to that in DESEP-B-colonized rats and was significantly more severe than E. coli-induced colitis, which was absent by histological testing and mild by colonic myeloperoxidase and interleukin-1β concentration determinations. However, gastritis was detectable only in DESEP-B-associated rats. These studies suggest that not all resident bacteria have equal proinflammatory capabilities, since B. vulgatus alone is more active than E. coli alone in inducing colitis, and that colitis and gastritis result from different luminal bacterial stimuli.

Purification and Properties of NADH-Dependent 5,10-Methylenetetrahydrofolate Reductase (MetF) fromEscherichia coli

ABSTRACT A K-12 strain of Escherichia coli that overproduces methylenetetrahydrofolate reductase (MetF) has been constructed, and the enzyme has been purified to apparent homogeneity. A plasmid specifying MetF with six histidine residues added to the C terminus has been used to purify histidine-tagged MetF to homogeneity in a single step by affinity chromatography on nickel-agarose, yielding a preparation with specific activity comparable to that of the unmodified enzyme. The native protein comprises four identical 33-kDa subunits, each of which contains a molecule of noncovalently bound flavin adenine dinucleotide (FAD). No additional cofactors or metals have been detected. The purified enzyme catalyzes the reduction of methylenetetrahydrofolate to methyltetrahydrofolate, using NADH as the reductant. Kinetic parameters have been determined at 15°C and pH 7.2 in a stopped-flow spectrophotometer; the Km for NADH is 13 μM, the Km for CH2-H4folate is 0.8 μM, and the turnover number under V max conditions estimated for the reaction is 1,800 mol of NADH oxidized min−1 (mol of enzyme-bound FAD)−1. NADPH also serves as a reductant, but exhibits a much higher Km . MetF also catalyzes the oxidation of methyltetrahydrofolate to methylenetetrahydrofolate in the presence of menadione, which serves as an electron acceptor. The properties of MetF from E. coli differ from those of the ferredoxin-dependent methylenetetrahydrofolate reductase isolated from the homoacetogen Clostridium formicoaceticum and more closely resemble those of the NADH-dependent enzyme fromPeptostreptococcus productus and the NADPH-dependent enzymes from eukaryotes.