Study on the effect of organophosphate esters flame retardants in marine bacterial isolates under different growth conditions
Microbial biogeochemistry, including biodegradation, shapes the environmental fate of organophosphate ester flame retardants and plasticizers (OPE), ubiquitous contaminants with known toxic effects in the marine environment. However, the relative importance of these response pathways, and the environmental factors regulating them, remain poorly understood. Here, we investigated the capacity of marine bacteria to tolerate and biodegrade environmentally relevant OPE and examined the microbial physiological and transcriptional responses. Enrichment experiments from Antarctic and North Atlantic waters yielded 697 bacterial isolates spanning eight taxonomic orders. A subset of isolates was screened for growth and degradation of six common OPE under replete, carbon- and phosphorus-limited conditions. Approximately 60% of the strains degraded >20% of at least one OPE within 48 h, with marked strain- and compound-specific patterns. Haloalkyl OPE (TCEP, TCPP) were preferentially degraded relative to aryl compounds, and degradation was generally enhanced under carbon limitation, indicating potential use of OPE as a carbon source. Transcriptomic analyses of Salipiger sp. CULT_670 showed that OPE exposure induced distinct nutrient-dependent gene expression responses. Under repleted (non-limited) conditions, OPE triggered a broad stress response with down-regulation of energy-intensive pathways and up-regulation of amino acid, nucleotide, and cofactor biosynthesis. Under carbon limitation, OPE exposure intensified transcriptional repression of central carbon metabolism, whereas phosphorus limitation induced Type VI secretion system genes. Together, these results demonstrate that OPE biodegradation by marine bacteria is taxon-, compound-, and nutrient-dependent, and that microbial stress responses, rather than specialized catabolic pathways, might dominate transcriptional regulation under OPE exposure, as well OPE degradation.
Microbial biogeochemistry, including biodegradation, shapes the environmental fate of organophosphate ester flame retardants and plasticizers (OPE), ubiquitous contaminants with known toxic effects in the marine environment. However, the relative importance of these response pathways, and the environmental factors regulating them, remain poorly understood. Here, we investigated the capacity of marine bacteria to tolerate and biodegrade environmentally relevant OPE and examined the microbial physiological and transcriptional responses. Enrichment experiments from Antarctic and North Atlantic waters yielded 697 bacterial isolates spanning eight taxonomic orders. A subset of isolates was screened for growth and degradation of six common OPE under replete, carbon- and phosphorus-limited conditions. Approximately 60% of the strains degraded >20% of at least one OPE within 48 h, with marked strain- and compound-specific patterns. Haloalkyl OPE (TCEP, TCPP) were preferentially degraded relative to aryl compounds, and degradation was generally enhanced under carbon limitation, indicating potential use of OPE as a carbon source. Transcriptomic analyses of Salipiger sp. CULT_670 showed that OPE exposure induced distinct nutrient-dependent gene expression responses. Under repleted (non-limited) conditions, OPE triggered a broad stress response with down-regulation of energy-intensive pathways and up-regulation of amino acid, nucleotide, and cofactor biosynthesis. Under carbon limitation, OPE exposure intensified transcriptional repression of central carbon metabolism, whereas phosphorus limitation induced Type VI secretion system genes. Together, these results demonstrate that OPE biodegradation by marine bacteria is taxon-, compound-, and nutrient-dependent, and that microbial stress responses, rather than specialized catabolic pathways, might dominate transcriptional regulation under OPE exposure, as well OPE degradation.
Institute of Environmental Assessment and Water Research