Biostimulation of Resident Bacteria flora from Freshwater during Biodegradation of Organotin Compounds

Water samples obtained from five (5) locations along River Benue were spiked with organotin (TBTCl) in a ratio of 3mM to 1 liter. Two nutrient amendments (NPK fertilizer and poultry dung) were added to stimulate bacterial activity as degradation set up of 3 treatments including a control was monitored for 56 days. Organotin degradation activity was measured by monitoring decrease in TBTCl using X-ray fluorescence spectrometer on day 0, 14, 28, 42 and 56. Test chemical concentrations as well as microbial counts were recorded accordingly. Bacteria which demonstrated consistent growth in the presence of test organotin after 56 days were screened for organotin resistance potential by culturing on MSA medium containing varying concentrations of test organotins; 5 mM, 7 mM, and 10 mM. Organotin utilizing bacteria from fresh water were molecularly characterized and sequenced using pacBio sequencing. Degradation experiment showed an initial increase in microbial growth with counts hitting peak values on the 28th day after which microbial counts continuously dropped until the 56th day. There was a corresponding reduction in the concentration of the test organotin from 350 mg/L on day 0 to an average of 66.78 mg/L on day 56 indicating an average of 81.67% reduction. Organotin degradation by bacteria was significant p < 0.05 (One Way Anova) and Pearson correlation analysis showed a significant relationship between decrease in test organotins and bacterial growth (r = -215; p = 1.33). Metagenomic results showed that 76.27% of bacteria capable of organotin utilization belong to the phylum Proteobacteria. Azospira spp 36% was identified as a potent organotin degrader while commamonas spp 6.7%, Sedimentibaacter spp 3%, Clostridium bowmanii 2.66% and Serpens flexibilis 2.08% , demonstrated only mild growth. Rate of degradation of test organotins was faster when stimulated with NPK fertilizer compared to poultry dung. Further research on large scale, on-site biostimulation strategies is highly advocated.