The Mycobacterium tuberculosis H37Rv efpA gene encodes a putative efflux protein, EfpA, of 55,670 Da. The deduced EfpA protein was similar in secondary structure to Pur8, MmrA, TcmA, LfrA, EmrB, and other members of the QacA transporter family (QacA TF) which mediate antibiotic and chemical resistance in bacteria and yeast. The predicted EfpA sequence possessed all transporter motifs characteristic of the QacA TF, including those associated with proton-antiport function and the motif considered to be specific to exporters. The 1,590-bp efpA open reading frame was G؉C rich (65%), whereas the 40-bp region immediately upstream had an A؉T bias (35% G؉C). Reverse transcriptase-PCR assays indicated that efpA was expressed in vitro and in situ. Putative promoter sequences were partially overlapped by the A؉T-rich region and by a region capable of forming alternative secondary structures indicative of transcriptional regulation in analogous systems. PCR single-stranded conformational polymorphism analysis demonstrated that these upstream flanking sequences and the 231-bp, 5 coding region are highly conserved among both drug-sensitive and multiply-drug-resistant isolates of M. tuberculosis. The efpA gene was present in the slow-growing human pathogens M. tuberculosis, Mycobacterium leprae, and Mycobacterium bovis and in the opportunistic human pathogens Mycobacterium avium and Mycobacterium intracellular. However, efpA was not present in 17 other opportunistically pathogenic or nonpathogenic mycobacterial species.
SYNOPSIS. The temporal separation of macromolecular syntheses from protein assembly into microtubular structures has permitted the use of the Stentor ciliated oral membranellar band regenerating system as an assay for mitotic spindle inhibitors (Banerjee & Margulis, 1971). Melatonin, the pineal gland hormone, is additive to Colcemid in this assay; like Colcemid it specifically inhibits band migration as a sensitive function of developmental stage and concentration. Altho the entire process of band formation and cilia regeneration (stages 0–8) is inhibited by melatonin, stage 3 is especially sensitive. Delay in morphogenesis at stage 3 can be measured as a precise function of inhibitors (Colcemid, podophyllotoxin, melatonin) of the form y=kxn, where y is delay in hours and k is the concentration of inhibitor in moles. Riboflavin (0.2 μM) and nicotinamide (0.2 μM) in combination reversed Colcemid‐induced delay in band regeneration, but (unlike melatonin) the vitamins alone were totally without effect on the regenerating system. Therefore melatonin probably interacts with microtubule protein whereas the B vitamins interact in some way with Colcemid to nullify its activity.
SUMMARY : Salmonella, shigella, alkalescens-dispar, proteus, paracolon and coliform strains were tested for the presence of a coagulase enzyme as manifested by the ability to clot plasma. The shigella and proteus strains examined gave negative results ; a high percentage of the remaining strains clotted citrated plasma but this reaction was due to metabolism of citrate and subsequent liberation of calcium ions and not to a coagulase enzyme. Results depended on the bacterial strain and on the kind and dilution of plasma used. Utilization of citrate in citrated plasma was compared with the ability of the tested strains to attack citrate in Koser's ammonium citrate medium and in sodium citrate peptone medium. The Shigella and Proteus species examined failed to utilize citrate in any of the media under the conditions of the tests, Salmonella species gave fairly uniform results in the three media, while paracolon, coliform and alkalescens-dispar strains differed in their activity, the highest percentage of positive reactions being obtained in plasma-containing media.In the course of a study of Gram-negative bacilli these organisms were examined to see whether they possessed coagulases capable of clotting plasma. A survey of literature showed that numerous bacterial species have been examined for plasma-coagulating ability. Conflicting results have been obtained, due possibly to different experimental conditions. In the present communication only intestinal Gram-negative bacilli will be considered.Loeb (
Proteins which are secreted or associated with the cell envelope of Mycobacterium tuberculosis may contain protective T-cell epitopes. Prior to this study, a recombinant clone bank of enzymatically active M. tuberculosis-alkaline phosphatase fusions, were screened for immunogenicity in a murine T-cell model. Five of these were selected for further study, and the IFN-gamma secretion and proliferation of human PBMC from purified protein derivative- (PPD)-positive and PPD-negative donors were measured in response to oligopeptides, Mtb-PhoA fusions and one full-length protein. Epitopes from four of the five selected antigens were immunoreactive in the human model and corresponded to cytochrome d ubiquinol oxidase, cytochrome c oxidase subunit II, MTV005.02 and MTV033.08. Thus, this strategy identified novel human immunogenic peptides as possible candidates for a subunit vaccine.
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