Incidence of plasmid and antibiotic resistance in psychrotrophic bacteria isolated from Antarctic sponges

A total of 297 bacterial strains were isolated from five Antarctic sponge species and tested by agarose gel electrophoresis for the presence of plasmid molecules. At least one kind of plasmid was carried by 69 isolates (about 23%). The disc diffusion susceptibility test was used to assay the resistance of plasmid-harbouring bacteria towards 11 antibiotics. A multiple resistance was observed for the 72% of strains, among which the 33% were resistant to only two antibiotics. Bacteria showed a high degree of resistance towards O/129 (71%), tetracycline (42%) and nalidixic acid (25%), whereas any isolate showed resistance to gentamicin. The 16S rDNA sequencing revealed that plasmid-harbouring strains were mainly affiliated to the Gammaproteobacteria (81%), whereas the other detected phylogenetic groups (i.e. Firmicutes, Alphaproteobacteria, Actinobacteria and CFB group of Bacteroidetes) were less abundant, each representing between 1% and 6% of the total isolates. The present study will contribute to the poor and fragmentary knowledge on plasmid incidence in natural microbial populations. In addition, monitoring antibiotic resistance in bacteria from remote areas, such as Antarctica, could also be a useful tool to evaluate the impact of anthropic pressure

Ecophysiological characterization of cultivable Antarctic psychrotolerant marine bacteria able to degrade hydrocarbons

The basic understanding of both the physiology and ecology of psychrotolerant Antarctic bacteria is a crucial step for the optimization of their biodegradative activity in cold environments. The detection of cold-adapted hydrocarbon-degrading bacteria in Antarctic seawaters is certainly of great interest for bioremediative purpose in oil polluted marine Antarctic systems, where the introduction of non native species is not allowed. This study focused on psychrotolerant marine bacteria inhabiting an Antarctic coastal area directly influenced by the human activity at the Italian Research Station (Terra Nova Bay). Fifty bacterial strains were isolated from hydrocarbon-degrading enrichment cultures obtained from seawater samples collected in the inlet Road Bay (Ross Sea). A preliminary Restriction Fragment Length Polymorphism (RFLP) analysis, carried out on 16S rDNA amplified via PCR using RSAI and AluI restriction enzymes, was applied to cluster the isolates according to the restriction profile they showed. One representative isolate per cluster was selected for further characterization; to elucidate their taxonomic position, conventional phenotypic and phylogenetic analyses were performed. Results led to the identification of the isolates as members of ten genera belonging to four phylogenetic groups: the alfa- and gamma-proteobacteria subdivisions, the gram-positive branch and the Cytophaga-Flexibacter-Bacteroides (CFB) phylum. Results indicate a high degree of biodiversity within the peculiar ecophysiological group of the hydrocarbon-degrading marine bacteria

Ricerche sulla biodiversità delle comunità batteriche in tre laghi antartici

The bacterial diversity in three Antarctic lakes located at Crater Cirque (CC), Inexpressible Island (INI) and Luther Peak (LH) in the Victoria Land was investigated by a combination of culture-dependent and culture-independent techniques. The in situ abundance of different bacterial groups was determined by fluorescent in situ hybridization (FISH), while bacterial diversity among the cultivable microflora was investigated by culturing and genetic fingerprinting. Differences in the composition of bacterial assemblages were observed among the lakes investigated, when using the two approaches reported above. Overall, the detection rate by FISH of DAPI-stained cells varied from 48.4% to 68.9% with the general bacterial probe EUB338. Bacteria hybridizing with the group-specific probe CF319a were found to be abundant in the three lakes. A total of 478 strains were isolated from R2A agar plates and grouped by restriction analysis technique; sequencing of representative 16S rDNAs was performed to elucidate the taxonomic positions of isolates. Overall, isolates were placed within five different taxa: ?-Proteobacteria (39%), Bacteroidetes (35%), ?-Proteobacteria (8%), Actinobacteria (7%) and ?-Proteobacteria (5%). Finally, the 5.8% of total isolates shared the highest degree of sequence identity with unclassified bacteria. Members of the ?-Proteobacteria predominated at INI, whereas isolates from CC and LH mainly belonged to the Bacteroidetes. Among the ?-Proteobacteria, the genus Pseudomonas was predominant, whereas Flavobacterium spp. were very common among the Bacteroidetes. Finally, several Actinobacteria were closely related to unknown Antarctic bacteria

Microbial communities of recirculating aquaculture facilities (interaction between heterotrophic and autotrophic bacteria and the system itself)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceItalyFRI

Diesel oil and PCB-degrading psychrotrophic bacteria isolated from Antarctic seawaters (Terra Nova Bay, Ross Sea)

Fifty-seven Antarctic marine bacteria were examined for their ability to degrade commercial diesel oil as the sole organic substrate at both 4 °C and 20 °C. Based on the preliminary screening, two isolates (B11 and B15) with high capacity to degrade diesel oil were selected and their biodegradation effi ciency was quantifi ed by gas chromatographic analysis. As expected for psychrotrophs, diesel oil biodegradation was slower at 4 °C than at 20 °C. The two strains also mineralized the C28 n-paraffi n octacosane at 20 °C and polychlorinated biphenyls (PCBs) at 4 °C and 20 °C

Effects of a Simulated Acute Oil Spillage on Bacterial Communities from Arctic and Antarctic Marine Sediments

Background: The bacterial community responses to oil spill events are key elements to predict the fate of hydrocarbon pollution in receiving aquatic environments. In polar systems, cold temperatures and low irradiance levels can limit the effectiveness of contamination removal processes. In this study, the effects of a simulated acute oil spillage on bacterial communities from polar sediments were investigated, by assessing the role of hydrocarbon mixture, incubation time and source bacterial community in selecting oil-degrading bacterial phylotypes. Methods: The bacterial hydrocarbon degradation was evaluated by gas chromatography. Flow cytometric and fingerprinting profiles were used to assess the bacterial community dynamics over the experimental incubation time. Results: Direct responses to the simulated oil spill event were found from both Arctic and Antarctic settings, with recurrent bacterial community traits and diversity profiles, especially in crude oil enrichment. Along with the dominance of Pseudomonas spp., members of the well-known hydrocarbon degraders Granulosicoccus spp. and Cycloclasticus spp. were retrieved from both sediments. Conclusions: Our findings indicated that polar bacterial populations are able to respond to the detrimental effects of simulated hydrocarbon pollution, by developing into a more specialized active oil degrading community