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Energetics of Gliding Motility in Mycoplasma mobile. Jacob D. Jaffe, 2004.Mycoplasma mobile glides on surfaces at up to 7 µm/s by an unknown mechanism . We studied the energetics that power gliding by using a novel, growth medium-free system . We found that cells could glide in defined media if the glass substrate is preconditioned by exposure to horse serum . The active component that potentiates gliding is sensitive to proteinase K treatment . We used the defined medium system to test the effect of various inhibitors, ionophores, and poisons on motility of M . mobile . Valinomycin, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), N,N'-dicyclohexylcarbodiimide, phenamil, amiloride, rifampin, and puromycin had no short-term effects on gliding . We also confirmed that we were able to modulate the membrane potential with valinomycin and FCCP by using a potential-sensitive dye . Shifting the pH likewise had no effect on motility . These results rule out the use of conventional ion motive forces to power gliding . Arsenate had a dramatic inhibitory effect on gliding, and both the speed and the fraction of cells moving tracked ATP levels . Sodium orthovanadate had a slight but significant inhibitory effect on gliding . Taken together, these results suggest that the motor system of M . mobile is likely an ATPase or is directly coupled to an ATPase . Host-Adapted Cryptosporidium spp . in Canada Geese (Branta canadensis). Ling Zhou, 2004.The prevalence and distribution of Cryptosporidium spp . in the fecal droppings of the free-living waterfowl Canada geese were examined at 13 sites in Ohio and Illinois . On the basis of the analysis of the small-subunit rRNA gene by PCR, followed by restriction fragment length polymorphism analysis and DNA sequencing, 49 (23.4%) of 209 fecal specimens collected from 10 sites (76.9%) were positive for Cryptosporidium spp . The following five Cryptosporidium species and genotypes were identified: Cryptosporidium goose genotype I (in 36 specimens), Cryptosporidium goose genotype II (in 9 specimens), Cryptosporidium duck genotype (in 1 specimen), Cryptosporidium parvum (in 4 specimens), and C . hominis (in 2 specimens) . Cryptosporidium goose genotype I was the most prevalent parasite and was found at all five Cryptosporidium-positive sites in Ohio and at four of five positive sites in Illinois, followed by Cryptosporidium goose genotype II, which was found at two of five positive sites in Ohio and at four of five positive sites in Illinois . Cryptosporidium goose genotype II was detected for the first time, and it is phylogenetically related to goose genotype I and the duck genotype . All three genotypes have not so far been reported in humans, and their pathogenicity in geese has not been determined . Only 10.2% of the Cryptosporidium-positive specimens had C . parvum and C . hominis . The results of this study indicate that Canada geese might only serve as accidental carriers of cryptosporidia infectious to humans and probably play a minor role in the animal-to-human transmission cycle of the pathogen . Gene Expression Profiling of the pH Response in Escherichia coli. Don L. Tucker, 2002.Escherichia coli MG1655 acid-inducible genes were identified by whole-genome expression profiling . Cultures were grown to the mid-logarithmic phase on acidified glucose minimal medium, conditions that induce glutamate-dependent acid resistance (AR), while the other AR systems are either repressed or not induced . A total of 28 genes were induced in at least two of three experiments in which the gene expression profiles of cells grown in acid (pH 5.5 or 4.5) were compared to those of cells grown at pH 7.4 . As expected, the genes encoding glutamate decarboxylase, gadA and gadB, were significantly induced . Interestingly, two acid-inducible genes code for small basic proteins with pIs of >10.5, and six code for small acidic proteins with pIs ranging from 5.7 to 4.0; the roles of these small basic and acidic proteins in acid resistance are unknown . The acid-induced genes represented only five functional grouping categories, including eight genes involved in metabolism, nine associated with cell envelope structures or modifications, two encoding chaperones, six regulatory genes, and six unknown genes . It is unlikely that all of these genes are involved in the glutamate-dependent AR . However, nine acid-inducible genes are clustered in the gadA region, including hdeA, which encodes a putative periplasmic chaperone, and four putative regulatory genes . One of these putative regulators, yhiE, was shown to significantly increase acid resistance when overexpressed in cells that had not been preinduced by growth at pH 5.5, and mutation of yhiE decreased acid resistance; yhiE could therefore encode an activator of AR genes . Thus, the acid-inducible genes clustered in the gadA region appear to be involved in glutatmate-dependent acid resistance, although their specific roles remain to be elucidated . Role of the Stationary Growth Phase Sigma Factor RpoS of Burkholderia pseudomallei in Response to Physiological Stress Conditions. Benchamas Subsin, 2003.The Burkholderia pseudomallei rpoS gene was identified, and an rpoS null mutant was constructed . The mutant was shown to have an increased sensitivity to carbon starvation and oxidative stress . By using rpoS-lacZ fusions, transcription of rpoS was shown to be growth phase regulated, reaching a peak upon entry into stationary phase .
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