Bioprospecting of extremophilic perchlorate-reducing bacteria: report of promising Bacillus spp. isolated from sediments of the bay of Cartagena, Colombia.

Three extremophile bacterial strains (BBCOL-009, BBCOL-014 and BBCOL-015), capable of degrading high concentrations of perchlorate at a range of pH (6.5 to 10.0), were isolated from Colombian Caribbean Coast sediments. Morphological features included Gram negative strain bacilli with sizes averaged of 1.75 × 0.95, 2.32 × 0.65 and 3.08 × 0.70 µm, respectively. The reported strains tolerate a wide range of pH (6.5 to 10.0); concentrations of NaCl (3.5 to 7.5% w/v) and KClO4- (250 to 10000 mg/L), reduction of KClO4- from 10 to 25%. LB broth with NaCl (3.5-30% w/v) and KClO4- (250-10000 mg/L) were used in independent trials to evaluate susceptibility to salinity and perchlorate, respectively. Isolates increased their biomass at 7.5 % (w/v) NaCl with optimal development at 3.5 % NaCl. Subsequently, ClO4- reduction was assessed using LB medium with 3.5% NaCl and 10000 mg/L ClO4-. BBCOL-009, BBCOL-014 and BBCOL-015 achieved 10%, 17%, and 25% reduction of ClO4-, respectively. The 16 S rRNA gene sequence grouped them as Bacillus flexus T6186-2, Bacillus marisflavi TF-11 (T), and Bacillus vietnamensis 15 - 1 (T) respectively, with < 97.5% homology. In addition, antimicrobial resistance to ertapenem, vancomycine, amoxicillin clavulanate, penicillin, and erythromycin was present in all the isolates, indicating their high adaptability to stressful environments. The isolated strains from marine sediments in Cartagena Bay, Colombia are suitable candidates to reduce perchlorate contamination in different environments. Although the primary focus of the study of perchlorate-reducing and resistant bacteria is in the ecological and agricultural realms, from an astrobiological perspective, perchlorate-resistant bacteria serve as models for astrobiological investigations.

Biodegradation of biodiesel-oil by Cellulosimicrobium sp. Isolated from Colombian Caribbean soils.

Biodiesel is considered to be a natural substitute for fossil fuel. The comparatively low toxicity of biodiesel and its susceptibility to microbial biodegradation could reduce its environmental impact. Currently, biodiesel is sold previously mixed with petroleum-based hydrocarbons. The aim of this work was to measure the biodegradation potential of commercially available biodiesel, using bacterial strains (BBCOL-001, BBCOL-002, and BBCOL-003) isolated from a tropical forest soils in the Colombian Caribbean. According to nucleotide sequencing of the gene encoding for 16S rRNA, the strains belong to members of the genus Cellulosimicrobium. GC-MS analysis showed that biodiesel-oil alkanes were degraded by an average of 81.5% with optical density reaching 0.2-0.3 in minimal salt media at 37°C for 5 days. Individual diesel-oil alkanes were degraded by the strains at rates between 64.9% to 100%. The increase in bacterial biomass confirmed the use of the substrates by the microorganisms, suggesting these hydrocarbons are a carbon source. Changes in the biochemical behaviour of the strains suggested their capacity to adapt to environmental conditions might be an important resource for bioremediation.