Screening Of Bacteria Isolated From Earthworm Cast For Antibacterial Activities

4.1. DISCUSSION

The history of new drug discovery processes shows that novel skeletons have, in the majority of cases, come from natural sources (Bevan et al., 1995). This involves the screening of microorganisms and plant extracts, using a variety of models (Shadomy, 1987). In this scenario, it is important to screen bacteria from different unexplored habitats, which may prove to be the important sources of potent molecules. This study was focused on earthworm castings because earthworms redistribute organic matter within the soil, increase soil permeability and increase microbial activity by their burrowing and feeding activities (Syers & Springett, 2005). Hence, an effort had been made to explore the bacteria from earthworm castings for their antagonistic activity

The antibiotic - producing microorganism (antibacterial activity) isolated from the sample (earthworm castings) taken from the University of Nigeria, Nsukka and Odenigbo sampling Site was Bacillus spp. of all the bacterial species originally isolated. The results conform to many reviews of literature that Bacillus spp. are known to produce bioactive secondary metabolites (antibiotic). According to Prescott et al., (2008) spore forming bacteria and other members of the Bacillus genus possess genes for the catabolism of diverse carbon source and antibiotic synthesis. (Muaz & Shahida, 2010). in a research discovered the production of bacitracin and subtilin by Bacillus sp. Prescott et al., (2008) reported that Bacitracin produced by Bacillus sp. inhibits Escherichia coli and Staphylococcus aureus which corroborated the result in the present study. The other Bacterial isolates including Staphylococcus aureus, Enterococcus, and Micrococcus species were found to be incapable of exhibiting antibiotic activity against the various test organisms employed for antibiotic sensitivity testing.

This may be due to the fact that these strains of  bacterial  species  do  not  naturally have  the  tendency to  produce  antibiotic  substances. No actinomycetes antibiotic- producing organism was isolated. This is because the supposed agar and procedures were not used during this study. Also, Actinomycetes takes longer time to grow than the other bacteria as it has been reported by some literatures and this study did not work with that proximity of time.

CONCLUSION

The continuous use of antibiotics has resulted in a situation where the pathogens have acquired resistance against these antibiotics. So, now there is an urgent need for the development of a new line of novel, safe and effective antibiotics. Since, natural products have a novel structure; it remains as a major source of secondary metabolites. The present study, which was aimed to isolate soil microbes exhibiting antibacterial activity, yielded three isolates; IS2, IS7 and IS12 with significant zone of inhibition against the test human pathogens Staphylococcus aureus and Escherichia coli. This result can be further researched and modified and can be used commercially for the production of a new line of antibiotics after purification and proper standardization. This would help overcome the multidrug resistance of bacteria and pathogens generally.