Nadia Andreani, who visited the lab in 2105 (wow, time flies) and now is at the University of Lincolnnow is at the University of Lincoln has just published a paper on work she did here on blue, food-spoiling Pseudomonas. Colleague Lihong ZhangLihong Zhang is also on the paper, as he helped Naida with the transposon mutagenesis to pinpoint genes involved in blue pigment production. Very interestingly, the blue pigment (which is very reluctant to precise chemical characterisation but is an indole-derivateive) gives Pseudomonas increased resistance to oxidative stress, which potentially could aid survival in food insustry settings. It was great to have been involved in some Food Microbiology work and more projects are planned with Barbara Cardazzo’s group at the University of Padova. Below the Abstract:
Pseudomonas fluorescens Ps_77 is a blue-pigmenting strain able to cause food product discoloration, causing relevant economic losses especially in the dairy industry. Unlike non-pigmenting P. fluorescens, blue pigmenting strains previously were shown to carry a genomic region that includes homologs of trpABCDF genes, pointing at a possible role of the tryptophan biosynthetic pathway in production of the pigment. Here, we employ random mutagenesis to first identify the genes involved in blue-pigment production in P. fluorescens Ps_77 and second to investigate the biological function of the blue pigment. Genetic analyses based on the mapping of the random insertions allowed the identification of eight genes involved in pigment production, including the second copy of trpB (trpB_1) gene. Phenotypic characterization of Ps_77 white mutants demonstrated that the blue pigment increases oxidative-stress resistance. Indeed, while Ps_77 was growing at a normal rate in presence of 5 mM of H2O2, white mutants were completely inhibited. The antioxidative protection is not available for non-producing bacteria in co-culture with Ps_77.
Nadia Andrea Andreania, Lisa Carraroa, Lihong Zhang, Michiel Vos and Barbara Cardazzo. Transposon mutagenesis in Pseudomonas fluorescens reveals genes involved in blue pigment production and antioxidant protection. Food Microbiology in press https://doi.org/10.1016/j.fm.2019.03.028