ISOLATION AND IDENTIFICATION OF ANTIBIOTIC PRODUCING BACTERIA FROM SOIL
Abstract
Antibiotic resistance presents a growing global challenge, and soils are increasingly recognized as valuable reservoirs for bacteria capable of producing novel antimicrobial compounds. In light of this, the present study investigates the isolation of antibiotic-producing bacteria from different soil environments within Federal Polytechnic Bauchi, and evaluates their inhibitory effects against clinically relevant pathogens. Soil samples were collected from four distinct sites—farmland, dump site, biological garden, and hostel area—and subjected to serial dilution and culture on selective media. The isolates were characterized using Gram staining and standard biochemical assays, revealing species such as Bacillus spp., Staphylococcus aureus, and Escherichia coli. A statement of the problem driving this research is that the accumulation of resistant pathogens and lack of new antibiotics underscore an urgent need to explore environmental sources such as soil for novel antimicrobial agents. Among all isolates, only the Bacillus spp. strain exhibited measurable antibacterial activity. In agar diffusion assays, it produced inhibition zones of 18 mm against E. coli (moderate activity), 21 mm against S. aureus (strong activity), and 15 mm against Salmonella typhi. In contrast, the S. aureus and E. coli isolates derived from soil showed no inhibitory activity under the same conditions. These findings align with previous reports that soil-derived Bacillus species often display broad-spectrum antimicrobial activity, particularly against Gram-positive bacteria the results highlight that agricultural and waste soils within the study area harbor Bacillus strains with significant antibiotic-producing potential. Such isolates warrant further investigation, including purification of their bioactive compounds, minimum inhibitory concentration (MIC) determination, and molecular characterization of biosynthetic pathways. Unlocking these capabilities could contribute to the development of novel antibiotics and reinforce sustainable approaches to addressing antibiotic resistance.
Keywords: soil bacteria; Bacillus spp.; antibiotic production; agar diffusion; antimicrobial screening
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