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Increased ATPase Activity Is Responsible for Acid Sensitivity of Nisin-Resistant Listeria monocytogenes ATCC 700302. Jennifer Cleveland McEntire, 2004.The growth of the foodborne pathogen Listeria monocytogenes can be controlled by nisin, an antimicrobial peptide . A spontaneous mutant of L . monocytogenes shows both resistance to nisin and increased acid sensitivity compared to the wild type . Changes in the cell membrane correlated with nisin resistance, but the mechanism for acid sensitivity appears unrelated . When hydrochloric or lactic acid is added to cultures, intracellular ATP levels drop significantly in the mutant (P < 0.01) compared to the results seen with the wild type . Characterization of the F0F1 ATPase, which hydrolyzes ATP to pump protons from the cell cytoplasm, shows that the enzyme is more active in the mutant than in the wild type . These data support a model in which the increased activity of the mutant ATPase upon acid addition depletes the cells' supply of ATP, resulting in cell death . Periodicity of Cell Attachment Patterns during Escherichia coli Biofilm Development. Konstantin Agladze, 2003.The complex architecture of bacterial biofilms inevitably raises the question of their design . Microstructure of developing Escherichia coli biofilms was analyzed under static and laminar flow conditions . Cell attachment during early biofilm formation exhibited periodic density patterns that persisted during development . Several models for the origination of biofilm microstructure are considered, including an activator-inhibitor or Turing model . Identification of the Immunodominant Protein and Other Proteins of the Bacillus anthracis Exosporium. Christopher Steichen, 2003.Spores of Bacillus anthracis, the causative agent of anthrax, are enclosed by a prominent loose-fitting, balloon-like layer called the exosporium . Although the exosporium serves as the source of surface antigens and a primary permeability barrier of the spore, its molecular structure and function are not well characterized . In this study, we identified five major proteins in purified B . anthracis (Sterne strain) exosporia . One protein was the recently identified collagen-like glycoprotein BclA, which appears to be a structural component of the exosporium hair-like nap . Using a large panel of unique antispore monoclonal antibodies, we demonstrated that BclA is the immunodominant antigen on the B . anthracis spore surface . We also showed that the BclA protein and not a carbohydrate constituent directs the dominant immune response . In addition, the length of the central (GXX)n repeat region of BclA appears to be strain specific . Two other unique proteins, BxpA and BxpB, were identified . BxpA is unusually rich in Gln and Pro residues and contains several different tandem repeats, which also exhibit strain-specific variation . In addition, BxpA was found to be cleaved approximately in half . BxpB appears to be glycosylated or associated with glycosylated material and is encoded by a gene that (along with bclA) may be part of an exosporium genomic island . The other two proteins identified were alanine racemase and superoxide dismutase, both of which were reported to be associated with the surface of other Bacillus spores . Possible functions of the newly identified proteins are discussed .
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