Effect of Glyphosate Herbicide on the Bacterial Population of Arable Land in Keffi, Nasarawa State, Nigeria

The widespread use of herbicides in agriculture has raised significant concerns regarding their impact on the delicate balance of micro and macro flora and fauna in soil and human health. This study was aimed at effect of glyphosate herbicide on the bacterial population in arable land in Keffi, Topsoil samples were carefully collected from various locations in the Keffi arable land, and the bacteria present were isolated and identified using standard microbiological techniques. The results revealed a stark contrast in bacterial counts between the herbicide-polluted and non-polluted soil samples. In pot A, the bacterial count from the polluted soil was 9.3±1.33 CFU x 106, while the non-polluted soil had a count of 14.32±1.02 CFU x 106. Similarly, in pot B, the polluted soil had a bacterial count of 8.4±0.99 CFU x 106, compared to 13.01±1.54 CFU x 106 in the non-polluted soil. In pot C, the polluted soil had a bacterial count of 6.45±1.01 CFU x 106, while the non-polluted soil had 14.01±1.88 CFU x 106. The bacteria isolated from the different pots were also diverse in their composition. Pot A was dominated by Pseudomonas sp., Priestia sp., and Bacillus sp. (33.3% each), while pot B was dominated by Pseudomonas simiae (66.6%) and Proteus sp. and Bacillus magaterium (33.3% each). Pot C, was dominated by Bacillus sp. (66.6%) and Acinetobacter beijerinckii and Citrobacter sp. (33.3% each). Interestingly, several of the isolated bacteria, including Pseudomonas sp., Proteus sp and Acinetobacter beijerinckii, were able to survive and grow in the presence of the glyphosate herbicide. Pseudomonas sp. isolated from pot A1a exhibited the highest utilization of the herbicide, at 30°C (2.19±0.26 mg/ml) and the lowest at 26°C (1.23±0.11 mg/ml). Similar trends were observed for other isolates, with Proteus sp., Priestia sp., and Bacillus magaterium showing the highest herbicide utilization at 35°C. Pseudomonas simiae isolated from pot A1a demonstrated the highest utilization at pH 7.0 (3.54±0.32 mg/ml), and the lowest at pH 5.0 (1.68±0.57 mg/ml). Additionally, the same isolate showed the highest herbicide utilization after 4 and 5 weeks of incubation (2.08±0.02 mg/ml), and the lowest in week 1 (1.18±0.07 mg/ml). The findings of this comprehensive study clearly demonstrate the detrimental impact of glyphosate herbicide on the bacterial population in the arable land of Keffi, Nasarawa State.