Abilities of ındigenous microorganisms to utilise herbicides for growth and as carbon source ın-vitro

This study determined the abilities of indigenous microorganisms to utilise atrazine, xtravest, gramoxone and glyphosate as carbon source and for growth, which is a prerequisite for biodegradation and bioremediation of this herbicides in the soil. Soil treatments were carried out using the complete randomized block design for a period of 8 weeks; at company recommended rates of 4 l/h (at 350 ml in 15 l sprayer), soil treatments were carried out in triplicates. Isolation of microorganisms was done using the spread plate method on the solid mineral salts medium with each herbicide added to separate plates. The plates were incubated at 30°C for 5 days for bacteria and at 30oC for 7days for fungi. The ability of microbial isolates to utilise herbicide substrates in pure cultures were determined in minimal salt medium. B. subtilis, P. aeruginosa, P. florescences, P. putida, Aspergillus niger, A. tamarii, Fusarium oxysporum, and P. chrysogenum were isolated in all the herbicide treated soils. Bacillus subtilis recorded the highest optical density value of 1.401 on the 25th day and viable count value of 9.08 (1.21×109 cfu/ml) on the 20th day during growth on glyphosate. F. oxysporum recorded the lowest pH of 4 in gramoxone on the 25th day of incubation and the highest count of 6.10×104 cfu/g on the 20th day during atrazine utilisation. B. subtilis, A. niger and F. oxysporum showed the best abilities to utilise the herbicides for growth and as carbon source. Indigenous microorganisms used in this study successfully utilised the herbicides as carbon source and for growth. Indigenous microorganisms could be employed in the bioremediation of herbicide polluted soils. The ultimate success of bioremediation is dependent on microorganisms staying in close physical contact with substance to be degraded.