Project description:Pseudomonas aeruginosa is a common bacterium in the terminal plumbing system of buildings and it is from this niche that a substantial fraction of infections are acquired. To better understand P. aeruginosa biology in this environment, we examined the transcriptomes in tap water and pond water.
Project description:Many Pseudomonas aeruginosa infections are derived from residential, recreational, or surface water sources; thus, these environments represent an important preinfection niche. To better understand P. aeruginosa biology in these environments, we quantified transcriptional changes by microarray after exposure to diluted LB, diluted R2B, potable tap water, and freshwater from a eutrophic pond. Quantitative reverse transcription-PCR (qRT-PCR) confirmed the conservation of these responses in other water sources, and competition experiments were used to test the importance of three implicated metabolic pathways. The global transcriptional responses in potable water and freshwater showed strong induction of genes involved in metabolism of the head groups and acyl tails of phospholipids, as well as nucleotide metabolism, with commensurate decreased transcript expression of genes encoding their synthetic pathways. These data suggest that phospholipids and nucleotides are part of the nutritional milieu of these two environments. A unique response in municipal-delivered potable water was to the metals in the piping system, particularly copper. To identify potential nutrient sources used by P. aeruginosa in these environments, we used competition assays between the wild-type and deletion mutant strains in three pathways induced under these conditions. For phospholipid head-group metabolism, ethanolamine utilization (eutB) was important for competition in potable water, while choline oxidation (betBA) was important for competition in freshwater. Nucleotide utilization, particularly pyrimidine metabolism (dht), showed a trend toward importance in freshwater but was not statistically significant. These findings provide new insights into the P. aeruginosa response to potable water and freshwater and led to the identification of potentially important nutrient sources in these environments.IMPORTANCE Much of our knowledge about Pseudomonas aeruginosa comes from the infection niche, and much less is known about its lifestyle in the environment. P. aeruginosa is an adaptable bacterium capable of growing in many environments but is particularly common in potable water systems and freshwater. We used the transcriptional responses of P. aeruginosa to these environments to identify important nutrient sources specific to either of these two environments. Additionally, these environments could provide experimental situations to understand gene function for the large number of transcripts with unknown functions induced under these conditions.
Project description:In the search for sustainable drinking water, many countries are weighing up the benefits of advanced treatment technologies as a proactive measure to assist with the transformation of treated wastewater into a source of water used for the production of potable water. We investigated the biological effects along a pilot plant with an advanced water treatment process, using zebrafish embryos at different stages of development. The study took an innovative approach, comparing phenotypic observations with whole genome responses. This enabled us to keep an open mind about which chemicals might be influencing the biological activity. There was no evidence of acute toxicity at any stage of treatment, but distinctive abnormalities – skeletal, cardiovascular and pigmentation – occurred in a small proportion of embryos along the treatment process, and in a tap water, that were not detected in the aquarium water control. Reverse osmosis (RO) reduced the concentration of measured chemical contaminants in the water the most, whilst eliminating the occurrence of abnormalities detected in the fish. In contrast, advanced oxidation appeared to reverse the benefits of RO treatment by increasing the frequency of teratogenic and sub-lethal abnormalities seen in embryos. Genomic analysis found alterations to the retinoid system, which was consistent with the teratogenic abnormalities observed. In addition, we found evidence of changes to metabolic pathways, including tryptophan metabolism associated with the production of melatonin required for the control of normal circadian rhythms. Although we cannot extrapolate these preliminary findings in zebrafish embryos to human or environmental health, we show that underexplored forms of biological activity (that existing Test Guidelines are not designed to capture) occur in treated wastewater effluent, and/or may be created depending on the type of advanced treatment process used. Although the identity of the culprit chemicals are unknown at this time, our innovative approach highlights the need for more research into the effects of chemicals on the retinoid system (and metabolism).