Taketani and colleagues confirmed the importance of SRB populations in mangrove sediments, particularly after an oil-contamination event. In a study using mesocosms with pristine and polluted mangrove sediments, they reported an increase in SRB abundance in pristine sediment after oil input, and observed that a mangrove with history of oil Rabusertib cost contamination is better prepared to respond to such an adverse situation than a non-contaminated one . General bacterial abundance determined by 16S rRNA-targeted qPCR was highest in the 0–5 cm layer sediment, and decreased with depth (Figure 4). The same phenomenon occurs for sulphate-reducing bacteria, in agreement with sulphate concentrations selleck chemicals llc measured in the sediment depths investigated.
Comparing q-PCR results for dsr and 16S rRNA gene fragment genes suggests that a large fraction of the bacteria present may be sulphate-reducers.
It is remarkable that in the top sediment, dsr genes represent almost 80% of the number of genes for general bacteria (16S rRNA gene encoding fragment gene). For the deeper sediments these values are almost 40% (15–20 cm) and almost 65% (35–40 cm). It is well known that microorganisms contain more than one copy of 16S rRNA gene. This also might happen for dsr gene . Moreover, the primers for 16S rRNA gene encoding fragment gene used in the present study target bacteria, while in their study, Geets and colleagues  also detected archaeal dsr with the same primer pair that was used here. In principle dsr detected in these mangrove sediments by q-PCR could selleck products have archaeal species, and as such, N-acetylglucosamine-1-phosphate transferase the values we report could overestimate the number of sulphate-reducing bacteria. This is one of the few studies on anaerobic bacterial diversity in mangrove sediments at different sediment depths. Results presented in this study shows that the bacterial diversity and abundance change with depth. This might explain why petroleum and other xenobiotic compounds that percolate to the deep anoxic sediment layers may remain undegraded for years. Conclusions Sulphate decreases
dramatically in the first centimetres of the mangrove sediment, and overall bacterial diversity and abundance from the surficial interval (0–5 cm) differs from deeper layers (15–20 and 35–40 cm), which are very similar to each other. Genes involved in anaerobic alkane and aromatic petroleum hydrocarbon degradation were not detected by PCR, perhaps because gene targets for the PCR primers chosen may not have matched to in situ genetic diversity. Methods Sediment sampling The sampling site was the Suruí mangrove in Guanabara Bay, situated in Magé, state of Rio de Janeiro, Brazil (Figure 5). In the year 2000, there was an oil spill in Guanabara Bay, impacting the Suruí mangrove. More than 1 million liters of oil leaked from a broken pipeline of an oil refinery nearby, and the most affected region was the northern part of the bay . Figure 5 Suruí Mangrove location. Location of the Suruí Mangrove.