Thiocapsa marina sp. nov., a new purple sulfur bacterium containing okenone isolated from several brackish and marine environments

Four marine, phototrophic, purple sulfur bacteria (strains 5811T, 5812, BM-3 and BS-1) were isolated in pure culture from different brackish to marine sediments in the Mediterranean Sea, the White Sea and the Black Sea. Single cells of these strains were coccus-shaped, non-motile and did not contain gas vesicles. The colour of cell suspensions that were grown in the light was purple–red. Bacteriochlorophyll a and carotenoids of the okenone series were present as photosynthetic pigments. Photosynthetic membrane systems were of the vesicular type. Hydrogen sulfide, thiosulfate, elemental sulfur and molecular hydrogen were used as electron donors during photolithotrophic growth under anoxic conditions; carbon dioxide was utilized as the carbon source. During growth on sulfide, elemental sulfur globules were stored inside the cells. In the presence of hydrogen sulfide, several organic substances could be photoassimilated. Comparative 16S rDNA sequence analysis revealed an affiliation of these four strains to the genus Thiocapsa. Both phylogenetic analysis and the results of DNA–DNA hybridization studies revealed that these strains formed a separate cluster within the genus Thiocapsa. Thus, according to phenotypic characteristics and mainly the carotenoid composition, 16S rDNA sequence analysis and DNA–DNA hybridization data, it is proposed that these strains should be classified as a novel species, Thiocapsa marina sp. nov., with strain 5811T (=DSM 5653T=ATCC 43172T) as the type strain

Impact of a biorepair treatment on the diversity of calcifying bacterial communities at the surface of cracked concrete walls

International audienceChanges in the diversity of indigenous calcifying bacterial communities were determined before and after 1 year of biorepair treatment applied on indoor micro-cracked concrete walls. The biotreatment was based on the formation of an organo-mineral coating generated by Alkalihalobacillus pseudofirmus cultured in the presence of calcium lactate. Before and after the biotreatment, the calcifying bacterial strains belonging to either Firmicutes or Actinobacteria phylum were dominant depending on the sampling area. Nevertheless, the proportion of the calcifying Bacillus, Brachybacterium, Microbacterium, and Rhodococcus genera changed. These bacterial strains were likely to participate in the effectiveness of the biotreatment. Isolated bacteria of Microbacterium and Rhodococcus genera reported interesting calcifying capacity associated to microbial growth rates greater than the one observed for Alkalihalobacillus pseudofirmus. A bacterial consortium containing Alkalihalobacillus pseudofirmus, Rhodococcus cercidiphylli, and Microbacterium schleiferi demonstrated an improved calcifying capacity. Consequently, using a bacterial consortium instead of a single strain is an efficient way to improve the robustness of the biorepair treatment. Key points: • Indigenous calcifying bacteria mainly belonged to Firmicutes and Actinobacteria • Microbacterium and Rhodococcus reported the quickest growth rate with calcium lactate • A bacterial consortium with improved calcifying capacity is propose

Biodeterioration of mortars in sewers: relation with microbial diversity of biofilms

International audienceDeterioration of concrete in sewer systems is a worldwide pathology leading to premature aging of concrete pipes. Strong deterioration of concrete is mainly due to microorganisms, especially to sulfur-oxidizing bacteria (SOB) which produce sulfuric acid. Mortars made either with ordinary Portland cement (OPC) or calcium aluminate cement (CAC) have been exposed in a waste water collector for five years. Mortar microstructure was observed by microscopy with observations under scanning electron microscopy (SEM) to determine the thickness of the degraded zone. Moreover, the diversity of bacterial communities on biofilms collected at the mortar surface was characterized by using 16S rRNA sequencing. Microstructural approach demonstrated that CAC mortar was less deteriorated than OPC mortar when exposed for five years. Similar bacterial diversities were observed for OPC and CAC samples, but strong differences of relative abundance were evidenced. Both total bacterial and neutrophilic sulfur-oxidizing bacteria (NSOB) populations were smaller for CAC mortar compared to OPC mortar. In the reported in situ conditions, leading to the first stages of biodeterioration only involving NSOB, the better performance of mortar made with CAC is expected to be mainly due to lower abundances of both total bacterial and NSOB population at its surface. The lower abundance of NSOB in the biofilm formed at the mortar’s surface could be linked to the lower acid neutralization capacity of CAC mortar compared to OPC mortar when pH value is higher 4

Microbial degradation of hydrophobic emerging contaminants from marine sediment slurries (Capbreton Canyon) to pure bacterial strain

Despite emerging contaminants (ECs) are more and more monitored in environmental matrices, there is still lack of data in marine ecosystems, especially on their fate and degradation potentials. In this work, for the first time, the degradation potential of synthetic musks (galaxolide and tonalide), UV filters (padimate O and octo-crylene) and a pharmaceutical compound (carbamazepine) was studied in marine sediment samples, under laboratory conditions using sediment slurry incubations under biotic and abiotic conditions. Minimum half life times under biotic conditions were found at 21 days, 129 days and 199 days for padimate O, galaxolide and carbamazepine, respectively. Enrichments conducted under anoxic and oxic conditions demonstrated that degradations after one month of incubation either under both biotic and abiotic conditions were limited under anoxic conditions compared to oxic conditions for all the contaminants. Novel aerobic bacteria, able to degrade synthetic musks and UV filters have been isolated. These novel strains were mainly related to the Genus Bacillus. Based on these results, the isolated strains able to degrade such ECs, can have a strong implication in the natural resilience in marine environment, and could be used in remediation processes

Biodeterioration of mortars exposed to sewers in relation to microbial diversity of biofilms formed on the mortars surface

International audienceStrong deterioration of concrete in sewer systems is mainly due to microorganisms and especially to sulfur-oxidizing bacteria. Mortars made either with ordinary Portland cement (OPC) or calcium aluminate cement (CAC) were exposed in a waste water collector for five years. Mortar microstructure observed by microscopy reported a larger thickness of the degraded zone for OPC mortar. Taxonomic identification of bacterial communities performed on biofilms collected at the mortar surface reported similar bacterial diversities, but strong differences of relative abundance. A greater neutrophilic sulfur-oxidizing bacterial (NSOB) activity was observed for OPC mortar certainly in conjunction with its larger acid neutralization capacity. Thus, CAC mortar was less biodeteriorated than OPC mortar as less NSOB were able to settle on its surface in relation with its specific microstructure. The results of the reported field experiments have been compared with bioleaching laboratory experiments performed on identical mortars in the presence of Halothiobacillus neapolitanus as NSOB. As the deterioration mechanisms involved were similar, an acceleration factor with respect to the rate of in situ biodeterioration was determined for laboratory experiment

Transcriptomic evidence for versatile metabolic activities of mercury cycling microorganisms in brackish microbial mats

Methylmercury, biomagnifying through food chains, is highly toxic for aquatic life. Its production and degradation are largely driven by microbial transformations; however, diversity and metabolic activity of mercury transformers, resulting in methylmercury concentrations in environments, remain poorly understood. Microbial mats are thick biofilms where oxic and anoxic metabolisms cooccur, providing opportunities to investigate the complexity of the microbial mercury transformations over contrasted redox conditions. Here, we conducted a genome-resolved metagenomic and metatranscriptomic analysis to identify putative activity of mercury reducers, methylators and demethylators in microbial mats strongly contaminated by mercury. Our transcriptomic results revealed the major role of rare microorganisms in mercury cycling. Mercury methylators, mainly related to Desulfobacterota, expressed a large panel of metabolic activities in sulfur, iron, nitrogen, and halogen compound transformations, extending known activities of mercury methylators under suboxic to anoxic conditions. Methylmercury detoxification processes were dissociated in the microbial mats with methylmercury cleavage being carried out by sulfide-oxidizing Thiotrichaceae and Rhodobacteraceae populations, whereas mercury reducers included members of the Verrucomicrobia, Bacteroidetes, Gammaproteobacteria, and different populations of Rhodobacteraceae. However most of the mercury reduction was potentially carried out anaerobically by sulfur- and iron-reducing Desulfuromonadaceae, revising our understanding of mercury transformers ecophysiology

Bacterial periphytic communities related to mercury methylation within aquatic plant roots from a temperate freshwater lake (South-Western France)

cited By 0International audienceMacrophyte floating roots are considered as hotspots for methylmercury (MeHg) production in aquatic ecosystems through microbial activity. Nevertheless, very little is known about periphyton bacterial communities and mercury (Hg) methylators in such ecological niches. The ability to methylate inorganic Hg is broadly distributed among prokaryotes; however, sulfate-reducers have been reported to be the most important MeHg producers in macrophyte floating roots. In the present work, the periphyton bacterial communities colonizing Ludwigia sp. floating roots were investigated through molecular methods. Among the 244 clones investigated, anaerobic microorganisms associated with the sulfur biogeochemical cycle were identified. Notably, members of the sulfur-oxidizing prokaryotes and the anoxygenic, purple non-sulfur bacteria (Rhodobacteraceae, Comamonadaceae, Rhodocyclaceae, Hyphomicrobiaceae) and the sulfate reducers (Desulfobacteraceae, Syntrophobacteraceae, and Desulfobulbaceae) were detected. In addition, 15 sulfate-reducing strains related to the Desulfovibrionaceae family were isolated and their Hg-methylation capacity was tested using a biosensor. The overall results confirmed that Hg methylation is a strain-specific process since the four strains identified as new Hg-methylators were closely related to non-methylating isolates. This study highlights the potential involvement of periphytic bacteria in Hg methylation when favorable environmental conditions are present in such ecological micro-niches

Priority and emerging micropollutants in sediments of Capbreton Canyon (SW France)

International audiencePriority substances set by the Water Framework Directive (WFD) are of major interest to evaluate the quality of coastal and marine systems, the final receptors for pollutant emissions. Emerging substances not regulated by the WFD, i.e. personal care products and pharmaceuticals, are of high concern since only scarce information of their occurrence, reactivity and impact are available in themarine environment.A large screening of micropollutants has been achieved in surface sediments collected in the Canyon of Capbreton (Gulf of Biscay). Twenty-four stations have been sampled within the first 30 km of the canyon in July 2017. Occurrence andconcentrations of priority (PAHs, PCBs, OCPs and trace metal) and emerging micropollutants (synthetic musks and sunscreens compounds) have been determined. In addition, sediments collected at three different depths were used to perform incubation experiments with a synthetic musk (HHCB) or a sunscreen compound (OD-PABA). Experiments have been performed at 12°C in the dark, controls have been also conducted with sterilized sediments. Some priority substances were lower than the detection limits whereas PAHsand PCBs exhibited high concentration levels ranging from 199 to 7,116 ng.g-1 and from 0.1 to 18.6 ng.g-1, respectively. Emerging micropollutants were measured at low concentrations. Musk compounds (HHCB, AHTN and MK) concentrations were up to 3.6, 2.3 and 7.0 ng.g-1, respectively. Sunscreens (3-BC, 4-MBC, EHMC and OC) concentrations were up to 6.2, 9.2, 31.8 and 29.2 ng.g-1, respectively. Highest concentrations were observed for offshore stations. Sediments from terraces or slopes of the canyon exhibited higher levels compared to those from the continental shelf. Degradation potentials have been only observed under biotic condition for OD-PABA suggesting the involvement of biologically mediated mechanism

Dynamics of microbial communities across the three domains of life in the Bay of Biscay with emphasis on marine mucilage

National audienc

Effect of macrofaunal bioturbation on bacterial distribution in marine sandy sediments, with special reference to sulphur-oxidising bacteria

cited By 33International audienceWe have studied the impact of the bioturbating macrofauna, in particular the lugworm Arenicola marina and the bivalve Cerastoderma edule, on abundances and distribution patterns of total bacteria and of bacteria of selected functional groups in sandy intertidal sediments. The selected groups comprised the colourless sulphur-oxidising bacteria and the anoxygenic phototrophic bacteria, which are expected to occupy small zones at the oxygen-sulphide interface in stable (non-bioturbated) sediments. The presence of a wooden wreck buried in the sediment at 10 cm depth within a large area of intertidal sand flat colonised by lugworms provided a unique opportunity to confront field observations with laboratory simulations. The site with the wooden wreck, which was used as control site, was devoid of both A. marina and C. edule, while the composition of the rest of the zoobenthic community was rather similar to that of the surrounding area. In the field, the density of total bacteria was approximately one order of magnitude higher in the control site than in the natural (bioturbated) site. This can be explained by the higher contents of silt and clay particles (higher surface-area/volume ratio) and higher total organic-carbon contents found at the control site. It appears that the presence of macrofauna affects sedimentation processes, which indirectly influence bacterial dynamics. Samples from the control site have been incubated in the laboratory with A. marina and C. edule added (bioturbated core), while an unamended core served as a control. The laboratory experiments contrasted with the field observations, because it was found that total bacteria were actually higher in the deeper layers of the bioturbated core. Moreover, the populations were more homogeneous (less stratified) and colourless sulphur bacteria were on average less numerous in the bioturbated core. In general, laboratory incubations resulted in a decrease of total bacteria with a concomitant increase of colourless and phototrophic sulphur-oxidising bacteria and thus in modifications of the bacterial community structure. Hence, our results demonstrate that care must be taken in extrapolating results from laboratory experiments (e.g. mesocosm research) to field situations