Genes Involved in Yellow Pigmentation of Cronobacter sakazakii ES5 and Influence of Pigmentation on Persistence and Growth under Environmental Stress

Abstract

Cronobacter spp. are opportunistic food-borne pathogens that are responsible for rare but highly fatal cases of meningitis and necrotizing enterocolitis in neonates. While the operon responsible for yellow pigmentation in Cronobacter sakazakii strain ES5 was described recently, the involvement of additional genes in pigment expression and the influence of pigmentation on the fitness of Cronobacter spp. have not been investigated. Thus, the aim of this study was to identify further genes involved in pigment expression in Cronobacter sakazakii ES5 and to assess the influence of pigmentation on growth and persistence under conditions of environmental stress. A knockout library was created using random transposon mutagenesis. The screening of 9,500 mutants for decreased pigment production identified 30 colorless mutants. The mapping of transposon insertion sites revealed insertions in not only the carotenoid operon but also in various other genes involved in signal transduction, inorganic ions, and energy metabolism. To determine the effect of pigmentation on fitness, colorless mutants (⌬crtE, ⌬crtX, and ⌬crtY) were compared to the yellow wild type using growth and inactivation experiments, a macrophage assay, and a phenotype array. Among other findings, the colorless mutants grew at significantly increased rates under osmotic stress compared to that of the yellow wild type while showing increased susceptibility to desiccation. Moreover, ⌬crtE and ⌬crtY exhibited increased sensitivity to UVB irradiation.

Erwinia gerundensis sp. nov., a cosmopolitan epiphyte originally isolated from pome fruit trees

“…S6). This genetic setting is common to species of the genus Cronobacter (Johler et al, 2010) and was also found in the genomes of Pantoea sp. IMH (Tian & Jing, 2014) and Pantoea sp.…”

Genes Involved in Cronobacter sakazakii Biofilm Formation

“…Southern analysis was performed as described previously (21). For identification of insertion sites by the subcloning procedure, chromosomal DNA of the transposon mutants was digested with SphI, and the fragments were ligated into pUC18NotI (Table 1) digested with the same enzyme.…”

Cronobacter spp. – opportunistic food-borne pathogens. A review of their virulence and environmental-adaptive traits

“…In addition, Edelson-Mammel et al (2006) reported that 10 out of 12 strains showed ,1 log decline at pH 3.5 over a 5 h incubation at 37 u C, whilst the most acid-sensitive strain showed~3.5 log decline. Johler et al (2010) showed that Cronobacter strains not only survived low pH, but were also able to grow to~10 9 c.f.u. ml 21 at pH 4.5 within 24 h. Overall, Cronobacter have a good potency to survive in acidic environments that may enable them to cope with stomach acidity.…”