Genetic Tools for the Manipulation of Moderately Halophilic Bacteria of the Family Halomonadaceae

Moderately halophilic bacteria of the family Halomonadaceae (Halomonas, Chromohalobacter , and Zymobacter ) have promising applications in biotechnology as a source of compatible solutes (stabilizers of biomolecules and cells), salt-tolerant enzymes, biosurfactants, and extracellular polysaccharides, among other products. In addition, they offer a number of advantages to be used as cell factories, alternative to conventional prokaryotic hosts like E. coli or Bacillus , for the production of recombinant proteins: (1) their high salt tolerance decreases to a minimum the necessity for aseptic conditions, resulting in cost-reducing conditions; (2) they are very easy to grow and maintain in the laboratory, and their nutritional requirements are simple; and (3) the majority can use a large range of compounds as a sole carbon and energy source. In this decade, the efforts of our group and others have made possible the genetic manipulation of this bacterial group. In this review, the most relevant tools are described, with emphasis given to cloning vectors, genetic exchange mechanisms, mutagenesis approaches, and reporter genes. Due to its relevance for genetic studies, complementary sections describing the influence of salinity on the susceptibility of moderately halophilic bacteria to antimicrobials, as well as the growth media most routinely used, culture conditions, and nucleic acid isolation procedures for these microorganisms, are included.