Isolation of hydrocarbonoclastic denitrifying bacteria from berre microbial mats

Facultative anaerobic bacteria were isolated from the chronically Polluted sediment from the Berre Lagoon after amendment with nitrate and octadecane or pristane. Seventy-one isolates were tested for their potential to utilize nitrate under anaerobic conditions and to degrade aerobically hydrocarbons rising a new agar plate test. The electrophoretic mobility of each amplified 16S rDNA fragment was performed by DGGE and each isolate was affiliated to a phylotype. Most of the isolates were denitrifiers or at least nitrate reducers and some heterogeneity of nitrate utilization among a 16S rDNA phylotype was observed. The addition of hydrocarbons resulted in a drastic change in the structure of the isolated strains. Most hydrocarbon potential degraders were restricted to few 16S rDNA phylotypes that remained or appeared between the two steps of the isolation procedure

Substrates specialization in lipid compounds and hydrocarbons of <i>Marinobacter</i> genus

International audienceThe impact of petroleum contamination and of burrowing macrofauna on abundances of Marinobacter and denitrifiers was tested in marine sediment mesocoms after 3 months incubation. Quantification of this genus by qPCR with a new primer set showed that the main factor favoring Marinobacter abundance was hydrocarbon amendment followed by macrofauna presence. In parallel, proportion of nosZ-harboring bacteria increased in the presence of marcrofauna. Quantitative finding were explained by physiological data from a set of 34 strains and by genomic analysis of 16 genomes spanning 15 different Marinobacter-validated species (Marinobacter hydrocarbonoclasticus, Marinobacter daeopensis, Marinobacter santoriniensis, Marinobacter pelagius, Marinobacter flavimaris, Marinobacter adhaerens, Marinobacter xestospongiae, Marinobacter algicola, Marinobacter vinifirmus, Marinobacter maritimus, Marinobacter psychrophilus, Marinobacter lipoliticus, Marinobacter manganoxydans, Marinobacter excellens, Marinobacter nanhaiticus) and 4 potential novel ones. Among the 105 organic electron donors tested in physiological analysis, Marinobacter pattern appeared narrow for almost all kinds of organic compounds except lipid ones. Strains of this set could oxidize a very large spectrum of lipids belonging to glycerolipids, branched, fatty acyls, and aromatic hydrocarbon classes. Physiological data were comforted by genomic analysis, and genes of alkane 1-monooxygenase, haloalkane dehalogenase, and flavin-binding monooxygenase were detected in most genomes. Denitrification was assessed for several strains belonging to M. hydrocarbonoclasticus, M. vinifirmus, Marinobacter maritinus, and M. pelagius species indicating the possibility to use nitrate as alternative electron acceptor. Higher occurrence of Marinobacter in the presence of petroleum appeared to be the result of a broader physiological trait allowing this genus to use lipids including hydrocarbon as principal electron donors