A 23.4 kb segment at the 69 degrees-70 degrees region of the Bacillus subtilis genome

Transcriptional regulation, occurrence and putative role of the Pht family of Streptococcus pneumoniae

Restricted to the genus Streptococcus, the Pht protein family comprises four members: PhtA, PhtB, PhtD and PhtE. This family has the potential to provide a protein candidate for incorporation in pneumococcal vaccines. Based on sequence analysis and on RT-PCR experiments, we show here that the pht genes are organized in tandem but that their expression, except that of phtD, is monocistronic. PhtD, PhtE, PhtB and PhtA are present in 100, 97, 81 and 62 % of the strains, respectively, and, by analysing its sequence conservation across 107 pneumococcal strains, we showed that PhtD displays very little variability. To analyse the physiological function of these proteins, several mutants were constructed. The quadruple Pht-deficient mutant was not able to grow in a poor culture medium, but the addition of Zn(2+) or Mn(2+) restored its growth capacity. Moreover, the phtD mRNA expression level increased when the culture medium was depleted in zinc. Therefore, we suggest that these proteins are zinc and manganese scavengers, and are able to store these metals and to release them when the bacterium faces an ion-restricted environment. The data also showed that this protein family, and more particularly PhtD, is a promising candidate to be incorporated into pneumococcal vaccines.

Genetic organization of the lipopolysaccharide O-antigen biosynthetic locus of Leptospira borgpetersenii serovar Hardjobovis

Leptospiral LPS plays a critical role in immunity to leptospirosis and forms the basis for serological classification of Leptospira. However, neither the structure of leptospiral LPS nor the genetics of its biosynthesis have been elucidated. A probe derived from the rhamnose biosynthetic genes of L. interrogans serovar Copenhageni was used to identify the rfb locus of L. borgpetersenii serovar Hardjobovis. Chromosome walking and sequence analysis revealed an rfb locus spanning 36.7 kb, which consists of 31 ORFs transcribed in the same direction. Clusters of genes were identified which encode proteins related to enzymes involved in the biosynthesis of activated sugars including rhamnose. Additional ORFs in the locus encode glycosyltransferases for the assembly of the O-antigen subunit and integral membrane proteins for the transport of O-antigen subunits through the membrane and assembly into LPS.

The rfb genes in Azotobacter vinelandii are arranged in a rfbFGC gene cluster: a significant deviation to the arrangement of the rfb genes in Enterobacteriaceae

We report the identification of rfbF and rfbC located adjacent to the previously identified rfbG (Gavini et. al. Biochem. Biophys. Res. Commun. 1997, 240, 153-161) from the non-symbiotic, non-pathogenic soil bacterium Azotobacter vinelandii. The rfbF open reading frame encodes a putative polypeptide of 256 amino acids. This polypeptide shares a homology of 74% with the RfbF of Synechocystis sp. and a 70% homology with the AscA of Yersinia pseudotuberculosis which function as alpha-D-glucose-1-phosphate cytidylyltransferases in the biosynthesis of the O-antigen. The rfbC encodes a putative polypeptide of 186 amino acids. It shows strongest homology to the RfbC of Synechocystis sp. (64%) and Salmonella typhimurium (40%). RfbC functions as a dTDP-4-Dehydrorhamnose 3,5-Epimerase. The genes identified here have a low G + C content (approximately 56%) as compared to the A. vinelandii chromosome (approximately 63%) which is characteristic of the rfb clusters identified in other bacteria and may be indicative of the acquisition of the rfb genes by interspecific gene transfer. Despite the high level of sequence conservation, the organization of the rfb genes in A. vinelandii deviates from the arrangement of the most thoroughly studied rfb gene clusters of Enterobacteriaceae.

Identification and mutational analysis of rfbG, the gene encoding CDP-D-glucose-4,6-dehydratase, isolated from free living soil bacterium Azotobacter vinelandii

We have identified the rfbG from a non-symbiotic and non-pathogenic soil bacterium, Azotobacter vinelandii. The nucleotide sequence analysis of the rfbG revealed an open reading frame that encodes a peptide of 360 amino acids. This deduced peptide shares 57% homology with the RfbG of Synechocystis and 47% homology with the RfbG of Yersinia pseudotuberculosis. The previously identified short-chain dehydrogenases/reductases family signature sequence is conserved in the sequence of the RfbG of A. vinelandii. Southern blotting analysis of A. vinelandii chromosome by probed with 1.1 kb PstI DNA fragment corresponding to rfbG revealed that it is present as single copy on A. vinelandii chromosome. Disrupting the rfbG present on the chromosome of A. vinelandii, by insertion of kanamycin resistance marker via homologous recombination, resulted in drastic changes in the growth characteristics. The rfbG-negative A. vinelandii grown in liquid medium exhibited agglutination that is characteristic of rfb- mutants of other bacteria, suggesting that we have cloned the functional copy of the rfbG of A. vinelandii.

Cloning and sequencing of a 35.7 kb in the 70 degree-73 degree region of the Bacillus subtilis genome reveal genes for a new two-component system, three spore germination proteins, an iron uptake system and a general stress response protein

In the framework of the international project aimed at sequencing the Bacillus subtilis (Bs) genome, a 35.7-kb chromosome segment around the pel locus has been cloned and sequenced. This region (35,745 bp; 70 degrees-73 degrees of the genetic map) contains two partial and 38 complete orfs. A homology search for the products deduced from the 39 orfs revealed that 26 of them exhibit significant similarity to known proteins, e.g. germination proteins, sodium-alanine symporter, PTS system, methionine amino peptidase, 2-oxoglutarate/malate translocater, pectate lyase, general stress response protein, RNA helicase, iron uptake and two-component systems.