cse , a Chimeric and Variable Gene, Encodes an Extracellular Protein Involved in Cellular Segregation in Streptococcus thermophilus

Abstract

The isolation of a Streptococcus thermophilus CNRZ368 mutant displaying a long-chain phenotype allowed us to identify the cse gene (for cellular segregation). The N terminus of Cse exhibits high similarity to Streptococcus agalactiae surface immunogenic protein (SIP), while its C terminus exhibits high similarity to S. thermophilus PcsB. In CNRZ368, deletion of the entire cse open reading frame leads to drastic lengthening of cell chains and altered colony morphology. Complementation of the ⌬cse mutation with a wild-type allele restored both wild-type phenotypes. The central part of Cse is a repeat-rich region with low sequence complexity. Comparison of cse from CNRZ368 and LMG18311 strains reveals high variability of this repeat-rich region. To assess the impact of this central region variability, the central region of LMG18311 cse was exchanged with that of CNRZ368 cse. This replacement did not affect chain length, showing that divergence of the central part does not modify cell segregation activity of Cse. The structure of the cse locus suggests that the chimeric organization of cse results from insertion of a duplicated sequence deriving from the pcsB 3 end into an ancestral sip gene. Thus, the cse locus illustrates the module-shuffling mechanism of bacterial gene evolution.

Role of Peptidoglycan Amidases in the Development and Morphology of the Division Septum in Escherichia coli

“…In B. subtilis, the absence of the LytE murein hydrolase produces curved or bent cells that have unnatural lengths and widths (9). Removal of the PcsB protein, which has the characteristics of a murein hydrolase active during cell separation (7,39), causes similarly aberrant cell division in several streptococci. A pcsB mutant of Streptococcus agalactiae grows in clumps because division septa are placed at unnatural (tilted) angles that produce "kinked" chains of cells whose size and shape are not uniform (41,42).…”

“…An S. pneumoniae pcsB mutant grows in long chains with multiple misplaced, tilted, aberrant, and unordered septa that create dramatically kinked chains (36). Streptococcus mutans lacking its pcsB homologue (sagA) produces misshapen cells with aberrant and "wavy" septal ingrowth and placement (11), and Streptococcus thermophilus deleted of its homologue (cse) grows in extremely long chains (7).…”

Defects in ex vivo and in vivo growth and sensitivity to osmotic stress of group A Streptococcus caused by interruption of response regulator gene vicR

“…A third possibility is that PcsB may not be essential in GAS. PcsB is essential in S. pneumoniae (Ng et al, 2004) and Enterococcus faecium (Teng et al, 2003), but not in Streptococcus agalactiae, S. mutans or Streptococcus thermophilus (Reinscheid et al, 2001;Chia et al, 2001;Borges et al, 2005). Thus, GAS PcsB may not be essential.…”

Streptococcus pyogenes Ser/Thr Kinase-regulated Cell Wall Hydrolase Is a Cell Division Plane-recognizing and Chain-forming Virulence Factor

“…The purified SPy0019 has been previously reported to possess a human immunoglobulin binding ability and hence was termed as SibA (immunoglobulin-binding protein of group A Streptococcus) (18). Besides pneumococcal and group B streptococcal PcsB (15)(16)(17), SPy0019 is structurally similar to Streptococcal mutans GbpB/SagA (19), Streptococcus thermophilus Cse (20), Enterococcus faecalis/faecium (SalB/SagA) (21,22), and Listeria monocytogenes p45 protein (23). All of these proteins are involved in some way in the regulation of cell division.…”