DNA profiling of Stenotrophomonas maltophilia by PCR targeted to its species-specific repetitive palindromic sequences.

AIMS: The aim of this study was to develop a simple protocol for a PCR-based fingerprinting of Stenotrophomonas maltophilia (SmrepPCR) that utilizes primers complementary to repetitive extragenic palindromic elements (REPs) of this micro-organism. METHODS AND RESULTS: The relatedness of 34 isolates of environmental and clinical origin was investigated by two SmrepPCRs with two different primers, gyrB sequencing and XbaI macrorestriction followed by pulsed-field gel electrophoresis. While SmrepPCR (with primer DIR) results matched data obtained from the analysis of gyrB nucleotide sequences and identified several clonal complexes, XbaI macrorestriction showed high level of heterogeneity between isolates. The macrorestriction-based clustering of isolates did not correspond to both gyrB and DIR-SmrepPCR grouping. CONCLUSIONS: Our results show that SmrepPCR-inferred relationship of isolates is in a good agreement with sequence-based methods. The combined information from all methods used suggests that rapid evolution of S. maltophilia genomes might be predominantly due to high rate of rearrangements caused by mobile genetic elements. SIGNIFICANCE AND IMPACT OF THE STUDY: The presented method is an inexpensive and easy to perform alternative to genotype S. maltophilia isolates and to study their population genetics. SmrepPCR demonstrates the usefulness of species-specific repetitive elements in genomic analyses.

Mutation of a gene encoding a putative ribokinase leads to reduced salt tolerance under potassium limitation in Bacillus subtilis.

The Bacillus subtilis L-42 mutant strain, which displays limited growth and inability to cope with hyperosmotic shock in a defined medium with a K+ concentration of < 1 mmol/L, was isolated by non-specific transposon insertional mutagenesis followed by an enrichment selection in media with K+ concentration < 0.5 mmol/L. The growth rate (as the main physiological characteristic) was determined to test the viability of the isolated mutant in media with various concentrations of K+, different values of osmolarity and pH. The mutant revealed a significant decrease in growth rate when cultivated in media with K+ concentration < 1 mmol/L and at hyperosmolarity. Localization of the insertional mutation was provided, based on genetic characteristics of the used transposon. Only 1 insertion of recombinant transposon was found in the mutant chromosome, localized into the yxkO gene (a putative ribokinase with unknown biological function).

Characterization of phosphate transport in Streptomyces granaticolor.

Transport of inorganic phosphate in Streptomyces granaticolor was characterized in two growth stages; kinetic parameters were determined and two transport systems were found in both stages, with the following values: KT1 = 0.06 mM, Jlim1 = 0.95 nmol min-1 (mg DS)-1, and KT2 = 1.80 mM, Jlim2 = 25 nmol min-1 (mg DS)-1. Both systems require metabolic energy and substrates, such as sugars or polyols; when alanine was used or the energy source was omitted, the kinetic parameters changed in both systems. Both systems were inhibited by the ionophore cccp with identical k(i). KCN, an inhibitor or terminal cytochrome oxidase, inhibited the uptake of phosphate only partially, the uptake was inhibited completely when also the inhibitor of the alternative oxidative pathway (salicylhydroxamic acid) was added. Antimycin A inhibited the uptake completely. Arsenate inhibited competitively.