Identification of Klebsiella Variicola T29A Genes Involved In Tolerance To Desiccation

Several plant-beneficial bacteria have the capability to promote the growth of plants through different mechanisms. The survival of such bacteria could be affected by environmental abiotic factors compromising their capabilities of phytostimulation. One of the limiting abiotic factors is low water availability.

In extreme cases, bacterial cells can suffer desiccation, which triggers harmful effects on cells. Bacteria tolerant to desiccation have developed different strategies to cope with these conditions; however, the genes involved in these processes have not been sufficiently explored. Klebsiella variicola T29A is a beneficial bacterial strain that promotes the growth of corn plants and is highly tolerant to desiccation. In the present work, we investigated genes involved in desiccation tolerance.

As a result, a library of 8974 mutants of this bacterial strain was generated by random mutagenesis with mini-Tn5 transposon, and mutants that lost the capability to tolerate desiccation were selected. We found 14 sensitive mutants; those with the lowest bacterial survival rate contained mini-Tn5 transposon inserted into genes encoding a protein domain related to BetR, putative secretion ATPase and dihydroorotase. The mutant in the betR gene had the lowest survival; therefore, the mutagenized gene was validated using specific amplification and sequencing.

Trans complementation with the wild-type gene improved the survival of the mutant under desiccation conditions, showing that this gene is a determinant for the survival of K. variicola T29A under desiccation conditions.