|
|
|
|
|
|
Rescue of Social Motility Lost during Evolution of Myxococcus xanthus in an Asocial Environment. Gregory J. Velicer, 2002.Replicate populations of the social bacterium Myxococcus xanthus underwent extensive evolutionary adaptation to an asocial selective environment (liquid batch culture) . All 12 populations showed partial or complete loss of their social (S) motility function after 1,000 generations of evolution . Mutations in the pil gene cluster (responsible for type IV pilus biogenesis and function) were found to be at least partially responsible for the loss of S motility in the majority of evolved lines . Restoration (partial or complete) of S motility in the evolved lines by genetic complementation with wild-type pil genes positively affected their fruiting body development and sporulation while negatively affecting their competitive fitness in the asocial regime . This genetic tradeoff indicates that mutations in the pil region were adaptive in the asocial selective environment . This finding was confirmed by experiments showing that defined deletions of pil gene regions conferred a competitive advantage under asocial conditions . Moreover, an amino acid substitution in an evolved genotype was located in a region predicted by genetic complementation analysis to bear an adaptive mutation . The Products of the spoVA Operon Are Involved in Dipicolinic Acid Uptake into Developing Spores of Bacillus subtilis. Federico Tovar-Rojo, 2002.Bacillus subtilis cells with mutations in the spoVA operon do not complete sporulation . However, a spoVA strain with mutations that remove all three of the spore’s functional nutrient germinant receptors (termed the ger3 mutations) or the cortex lytic enzyme SleB (but not CwlJ) did complete sporulation . ger3 spoVA and sleB spoVA spores lack dipicolinic acid (DPA) and have lower core wet densities and levels of wet heat resistance than wild-type or ger3 spores . These properties of ger3 spoVA and sleB spoVA spores are identical to those of ger3 spoVF and sleB spoVF spores that lack DPA due to deletion of the spoVF operon coding for DPA synthetase . Sporulation in the presence of exogenous DPA restored DPA levels in ger3 spoVF spores to 53% of the wild-type spore levels, but there was no incorporation of exogenous DPA into ger3 spoVA spores . These data indicate that one or more products of the spoVA operon are involved in DPA transport into the developing forespore during sporulation . clpP of Streptococcus salivarius Is a Novel Member of the Dually Regulated Class of Stress Response Genes in Gram-Positive Bacteria. Arnaud Chastanet, 2003.Nucleotide sequence analysis of the Streptococcus salivarius clpP locus revealed potential binding sites for both the CtsR and HrcA repressors . Dual regulation by HrcA and CtsR was demonstrated by using Bacillus subtilis as a heterologous host, and CtsR was shown to bind directly to the clpP promoter sequence . This is the first example of a clpP gene under the control of HrcA .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
