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spoIVH (ykvV), a Requisite Cortex Formation Gene, Is Expressed in Both Sporulating Compartments of Bacillus subtilis. Daisuke Imamura, 2004.It is well known that the ykvU-ykvV operon is under the regulation of the  E-associated
RNA polymerase (EE) .
In our study, we observed that ykvV is transcribed together
with the upstream ykvU gene by EE
in the mother cell and monocistronically under EG
control in the forespore . Interestingly, alternatively expressed
ykvV in either the forespore or the mother cell increased the
sporulation efficiency in the ykvV background . Studies show
that the YkvV protein is a member of the thioredoxin superfamily and
also contains a putative Sec-type secretion signal at the N terminus .
We observed efficient sporulation in a mutant strain obtained
by replacing the putative signal peptide of YkvV with the secretion
signal sequence of SleB, indicating that the putative signal sequence
is essential for spore formation . These results suggest that YkvV is
capable of being transported by the putative Sec-type signal sequence
into the space between the double membranes surrounding the
forespore . The ability of ykvV expression in either
compartment to complement is indeed intriguing and further introduces
a new dimension to the genetics of B . subtilis spore
formation . Furthermore, electron microscopic observation revealed a
defective cortex in the ykvV disruptant . In addition, the
expression levels of
K-directed
genes significantly decreased despite normal
G
activity in the ykvV mutant . However, immunoblotting with the
anti-K
antibody showed that pro-K
was normally processed in the ykvV mutant, indicating that
YkvV plays an important role in cortex formation, consistent with
recent reports . We therefore propose that ykvV should be
renamed spoIVH .
Effects of Temperature and Salinity on Vibrio vulnificus Population Dynamics as Assessed by Quantitative PCR. Mark A. Randa, 2004.The abundance of Vibrio vulnificus in coastal environments has been linked to water temperature, while its relationship to salinity is less clear . We have developed a culture-independent, most-probable-number quantitative PCR approach to examine V . vulnificus population dynamics in Barnegat Bay, N.J . Based on the combined analysis of our results from Barnegat Bay and from the literature, the present data show that (i) V . vulnificus population dynamics are strongly correlated to water temperature and (ii) although the general trend is for V . vulnificus abundance to be inversely correlated with salinity, this relationship depends on salinity levels . Irrespective of temperature, high abundances of V . vulnificus are observed at 5 to 10 ppt, which thus appears to be the optimal salinity regime for their survival . At 20 to 25 ppt, V . vulnificus abundances show a positive correlation to salinity . Unsuccessful attempts to resuscitate V . vulnificus, combined with our inability to detect cells during the winter despite an assay adapted to detect viable but nonculturable (VBNC) cells, suggest that the decline and eventual disappearance of V . vulnificus from the water column during the winter months is due primarily to a significant reduction in population size and is not only the consequence of cells entering the VBNC state . These findings are in line with the hypothesis that the sediment serves as a refuge for a subpopulation of V . vulnificus over the winter and weather-driven mixing events during the spring initiate a summer bloom in the water column . Growth of a Dehalococcoides-Like Microorganism on Vinyl Chloride and cis-Dichloroethene as Electron Acceptors as Determined by Competitive PCR. Alison M. Cupples, 2003.A competitive PCR (cPCR) assay targeting 16S ribosomal DNA was developed to enumerate growth of a Dehalococcoides-like microorganism, bacterium VS, from a mixed culture catalyzing the reductive dehalogenation of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), with hydrogen being used as an electron donor . The growth of bacterium VS was found to be coupled to the dehalogenation of VC and cDCE, suggesting unique metabolic capabilities . The average growth yield was (5.2 ± 1.5) x 108 copies of the 16S rRNA gene/µmol of Cl- (number of samples, 10), with VC being used as the electron acceptor and hydrogen as the electron donor . The maximum VC utilization rate (  ) was determined to be 7.8 x 10-10 µmol of Cl- (copy-1 day-1), indicating a maximum growth rate of 0.4 day-1 . These average growth yield and
values agree well with values found previously for dechlorinating cultures . Decay coefficients were determined with growth (0.05 day-1) and no-growth (0.09 day-1) conditions . An important limitation of this cPCR assay was its inability to discriminate between active and inactive cells . This is an essential consideration for kinetic studies .
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