Novel role of the LPS core glycosyltransferase WapH for cold adaptation in the Antarctic bacterium Pseudomonas extremaustralis

Abstract

Psychrotroph microorganisms have developed cellular mechanisms to cope with cold stress. Cell envelopes are key components for bacterial survival. Outer membrane is a constituent of Gram negative bacterial envelopes, consisting of several components, such as lipopolysaccharides (LPS). In this work we investigated the relevance of envelope characteristics for cold adaptation in the Antarctic bacterium Pseudomonas extremaustralis by analyzing a mini Tn5 wapH mutant strain, encoding a core LPS glycosyltransferase. Our results showed that wapH strain is impaired to grow under low temperature but not for cold survival. The mutation in wapH, provoked a strong aggregative phenotype and modifications of envelope nanomechanical properties such as lower flexibility and higher turgor pressure, cell permeability and surface area to volume ratio (S/V). Changes in these characteristics were also observed in the wild type strain grown at different temperatures, showing higher cell flexibility but lower turgor pressure under cold conditions. Cold shock experiments indicated that an acclimation period in the wild type is necessary for cell flexibility and S/V ratio adjustments. Alteration in cell-cell interaction capabilities was observed in wapH strain. Mixed cells of wild type and wapH strains, as well as those of the wild type strain grown at different temperatures, showed a mosaic pattern of aggregation. These results indicate that wapH mutation provoked marked envelope alterations showing that LPS core conservation appears as a novel essential feature for active growth under cold conditions.

Psychrophilic lifestyles: mechanisms of adaptation and biotechnological tools

“…Finally, in common with that observed for other cell envelope components, transcriptome analyses have shown an upregulation of genes involved in biosynthesis of outer membrane components, with LPS biosynthetic genes (mainly glycosyltransferases) and outer membrane proteins being upregulated at low temperatures (De Maayer et al 2014;Frank et al 2011;Gao et al 2006). In agreement with this, a recent study showed how mutation of a core LPS glycosyltransferase gene (wapH) impaired growth of an Antarctic bacterium at low temperatures (Benforte et al 2018).…”

Reporting Key Features in Cold-Adapted Bacteria

“…In the Antarctic bacterium Pseudomonas syringae Lz4w, it was observed that low temperatures caused changes in the composition and fluidity of LPS as higher polymyxin B sensitivity was detected along with an increased amount of hydroxy fatty acids [ 58 ]. In another Antarctic Pseudomonas — P. extremaustralis —the relevance of the core integrity of the LPS to cope with cold was evidenced by analyzing a wapH mutant strain, encoding a core LPS glycosyltransferase [ 59 ]. The wapH strain was impaired to grow in the cold.…”

“…Changes in these characteristics were also observed when P. extremaustralis was grown at different temperatures. These results indicate that LPS appears as a novel essential feature for active growth under cold conditions [ 59 ].…”

Quantitative Analysis of Cold Stress Inducing Lipidomic Changes in Shewanella putrefaciens Using UHPLC-ESI-MS/MS

“…When S. putrefaciens was cultivated at 10, 4, and 0 • C, no significant differences (p > 0.05) in the content of total lipids and phospholipids were found among these three treatments. The importance of lipids composition in membranes for bacteria to survive under cold stress has been generally agreed [4,33,43]. Changes in lipids response to cold stress have been reported in different species of bacteria [2,44]; however, limited information is available on lipidomics, as stated in the Introduction.…”