A major autolysin of Pseudomonas aeruginosa: subcellular distribution, potential role in cell growth and division and secretion in surface membrane vesicles

Abstract

A 26-kDa murein hydrolase is the major autolysin of Pseudomonas aeruginosa PAO1, and its expression can be correlated with the growth and division of cells in both batch and synchronously growing cultures. In batch cultures, it is detected primarily during the mid-exponential growth phase, and in synchronous cultures, it is detected primarily during the cell elongation and division phases. Immunogold labeling of thin sections of P. aeruginosa using antibodies raised against the 26-kDa autolysin revealed that it is associated mainly with the cell envelope and in particular within the periplasm. It is also tightly bound to the peptidoglycan layer, since murein sacculi, isolated by boiling 4% sodium dodecyl sulfate treatment, could also be immunogold labeled. Since division is due to cell constriction in this P. aeruginosa strain (septa are rarely seen), we cannot comment on the autolysin's contribution to septation, although constriction sites were always heavily labeled. Some labeling was also found in the cytoplasm, and this was thought to be due to the de novo synthesis of the enzyme before translocation to the periplasm. Interestingly, the autolysin was also found to be associated with natural membrane vesicles which blebbed from the surface during cell growth; the enzyme is therefore part of the complex makeup of these membrane packages of secreted materials (J. L. Kadurugamuwa and T. J. Beveridge, J. Bacteriol. 177:3998-4008, 1995). The expression of these membrane vesicles was correlated with the expression of B-band lipopolysaccharide.

Membrane Vesicles Are Immunogenic Facsimiles of Salmonella typhimurium That Potently Activate Dendritic Cells, Prime B and T Cell Responses, and Stimulate Protective Immunity In Vivo

“…The essential nature of MV production is supported by the lack of reports for Gram negatives that fail to make MVs (MV-null) and that an Escherichia coli transposon library screened for MV production failed to produce MV-null mutants (3,4). These observations and the fact that MV production may be linked to bacterial replication (5,6) support at least two nonmutually exclusive models in which MV production is either intrinsic to bacterial growth/viability or a multigene process unaffected by single-gene mutations (3,7). Thus, despite a history of published reports spanning several decades, the mechanisms regulating MV production and formation are only beginning to be clarified (3, 6 -8).…”

“…Other groups report MV production to be an alternate secretion pathway capable of directing bacterial products, including cytotoxins (10,11), enzymes (5), and DNA (10,12), to prokaryotic and eukaryotic cells. For example, Helicobacter pylori produce vacuolating cytotoxin A-containing MVs (13,14), and E. coli and Salmonella typhi produce cytolysin A-containing MVs (15,16), which are cytotoxic to mammalian cells.…”

The cidA murein hydrolase regulator contributes to DNA release and biofilm development in Staphylococcus aureus

“…In P. aeruginosa, eDNA release depends on quorum sensing (35), and there is evidence to suggest that cell lysis itself may be achieved by prophage induction within a biofilm (38,50), or alternatively, as a consequence of the release of membrane vesicles that contain bacteriolytic activity (51,52) as well as DNA (53). In Streptococcus mutans and Streptococcus pneumoniae, DNA is released from a lysing subfraction of the bacterial population in response to competence development, a physiological process that also depends on quorum sensing (54)(55)(56)(57)(58)(59).…”

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

“…The LTs in P. aeruginosa were first identified using renaturing PAGE and zymograms [93,94]. A total of 11 LTs, MltA (PA1222), MltB (PA4444), MltD (PA1812), MltF (PA3764), MltF2 (PA2865), MltG (PA2963), Slt (PA3020), SltB2 (PA1171), SltH/SltB3 (PA3992) and RlpA (PA4000) were reported in P. aeruginosa [95][96][97][98][99].…”