The LPS core glycosyltransferase wabH is essential for cold growth in Pseudomonas extremaustralis

SOLAR VENERO EC; LOPEZ NANCY I; BENFORTE FLORENCIA; LIZARRAGA LEONARDO; COLONELLA MARIA ANTONELA; TRIBELLI PAULA M.

Congreso; XII Congreso Argentino de Microbiologia; 2017

SAMIGE

Temperature is a key factor for bacterial survival and growth. Although most of microorganism couldsuffer transient changes of temperature, the psycrophiles and psycrotolerant microorganism havedeveloped different adaptation strategies for growth under low temperatures. In Gram-negativebacteria, the lipopolysaccharide LPS is the major component of the outer membrane. In this work westudied the impact of a mutation in the gene wabH, encoding for a glycosyltransferase of the LPScore, in growth and survival under cold conditions in Pseudomonas extremaustralis, an Antarcticbacterium. Under low temperature, the wabH mutant strain was impaired to grow in solid and liquidcultures and to develop visible colonies and to grow in liquid cultures. Stress resistance assaysshowed that the oxidative stress resistance and the sensitivity to gentamycin was similar between thewild type and the mutant strain showing that the defect of growth under low temperatures was not duea pleiotropic phenotype. Additionally, we analyzed the envelope permeability in a SDS survival colonycount assay. The wabH strain showed lower resistance to SDS in comparison to the wild type strain(40.9±11.8 and 12.2±.0%, respectively) suggesting a more permeable state for the mutant strain.Additionally, Nanomechanical measurements using an atomic force microscopy were performed todetermine the biophysical behavior of the of the envelope, at 30oC for the wild type, the mutant andthe complemented strain and at 8oC for the wild type and the complemented strain. Thenanomechanical measurements showed that the mutation of wabH affects cell elasticity since thewabH strain presented a higher Young module value (E). These results suggest a more ?rigid? state inthe wabH strain than in the wild type. Additionally, the wild type strain presented differences betweentemperatures, showing a lower E value at 30oC in comparison with 8oC. Our results showed a keyrole of core LPS in cold adaptation by affecting cell elasticity.