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Force and Velocity of Mycoplasma mobile Gliding. Makoto Miyata, 2002.The effects of temperature and force on the gliding speed of Mycoplasma mobile were examined . Gliding speed increased linearly as a function of temperature from 0.46 µm/s at 11.5°C to 4.0 µm/s at 36.5°C . A polystyrene bead was attached to the tail of M . mobile using a polyclonal antibody raised against whole M . mobile cells . Cells attached to beads glided at the same speed as cells without beads . When liquid flow was applied in a flow chamber, cells reoriented and moved upstream with reduced speeds . Forces generated by cells at various gliding speeds were calculated by multiplying their estimated frictional drag coefficients with their velocities relative to the liquid . The gliding speed decreased linearly with force . At zero speed, the force measurements extrapolated to 26 pN at 22.5 and 27.5°C . At zero force, the speed extrapolated to 2.3 and 3.3 µm/s at 22.5 and 27.5°C, respectively—the same speeds as those observed for free gliding cells . Cells attached to beads were also trapped by an optical tweezer, and the stall force was measured to be 26 to 28 pN (17.5 to 27.5°C) . The gliding speed depended on temperature, but the maximum force did not, suggesting that the mechanism is composed of at least two steps, one that generates force and another that allows displacement . Other implications of these results are discussed . Identification of ZipA, a Signal Recognition Particle-Dependent Protein from Neisseria gonorrhoeae. Ying Du, 2003.A genetic screen designed to identify proteins that utilize the signal recognition particle (SRP) for targeting in Escherichia coli was used to screen a Neisseria gonorrhoeae plasmid library . Six plasmids were identified in this screen, and each is predicted to encode one or more putative cytoplasmic membrane (CM) proteins . One of these, pSLO7, has three open reading frames (ORFs), two of which have no similarity to known proteins in GenBank other than sequences from the closely related N . meningitidis . Further analyses showed that one of these, SLO7ORF3, encodes a protein that is dependent on the SRP for localization . This gene also appears to be essential in N . gonorrhoeae since it was not possible to generate null mutations in the gene . Although appearing unique to Neisseria at the DNA sequence level, SLO7ORF3 was found to share some features with the cell division gene zipA of E . coli . These features included similar chromosomal locations (with respect to linked genes) as well as similarities in the predicted protein domain structures . Here, we show that SLO7ORF3 can complement an E . coli conditional zipA mutant and therefore encodes a functional ZipA homolog in N . gonorrhoeae . This observation is significant in that it is the first ZipA homolog identified in a non-rod-shaped organism . Also interesting is that this is the fourth cell division protein (the others are FtsE, FtsX, and FtsQ) shown to utilize the SRP for localization, which may in part explain why the genes encoding the three SRP components are essential in bacteria . Isolation and Characterization of Campylobacter Bacteriophages from Retail Poultry. Robert J. Atterbury, 2003.The ability of phages to survive processing is an important aspect of their potential use in the biocontrol of Campylobacter in poultry production . To this end, we have developed a procedure to recover Campylobacter bacteriophages from chilled and frozen retail poultry and have validated the sensitivity of the method by using a characterized Campylobacter phage (i.e., NCTC 12674) . By using this method, we have shown that Campylobacter phages can survive on retail chicken under commercial storage conditions . Retail chicken portions purchased in the United Kingdom were screened for the presence of endogenous Campylobacter phages . Thirty-four Campylobacter bacteriophages were isolated from 300 chilled retail chicken portions, but none could be recovered from 150 frozen chicken portions . The phage isolates were characterized according to their lytic profiles, morphology, and genome size . The free-range products were significantly more likely to harbor phages (P < 0.001 by single-factor analysis of variance) than were standard or economy products . This study demonstrates that Campylobacter bacteriophages, along with their hosts, can survive commercial poultry processing procedures and that the phages exhibited a wide range of recovery rates from chicken skin stored at 4°C .
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