THE LPS CORE GLYCOSILTRANSFERASE wabH IS ESSENTIAL FOR COLD GROWTH IN Pseudomonas extremaustralis

BENFORTE, F.C.; SOLAR VENERO, E.C.; COLONELLA, A.; LIZARRAGA, L.; LÓPEZ, N.I.; TRIBELLI, P.M.

Tucuman

Congreso; XII Congreso de Microbiología General (SAMIGE); 2017

SAMIGE

Temperature is a key factor for bacterial survival and growth. Although most of microorganism could suffer transient changes of temperature, the psycrophiles and psycrotolerant microorganism have developed different adaptation strategies for growth under low temperatures. In Gram-negative bacteria, the lipopolysaccharide LPS is the major component of the outer membrane. In this work we studied the impact of a mutation in the gene wabH, encoding for a glycosyltransferase of the LPS core, in growth and survival under cold conditions in Pseudomonas extremaustralis, an Antarctic bacterium. 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 assays showed that the oxidative stress resistance and the sensitivity to gentamycin was similar between the wild 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 colony count 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 and the complemented strain and at 8oC for the wild type and the complemented strain. The nanomechanical measurements showed that the mutation of wabH affects cell elasticity since the wabH 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 between temperatures, showing a lower E value at 30oC in comparison with 8oC. Our results showed a key role of core LPS in cold adaptation by affecting cell elasticity.