ABSTRACT
In this study, we focussed on the isolation, enumeration, distribution and occurrence of rhizomicroflora of Musa sapientum var parasidiaca and Senna occidentalis. The population, occurrence and distribution of culturable bacteria, fungi and actinomycetes in 5, 10, 15, and 20 cm depths rhizosphere samples of Musa sapientum var parasidiaca and Senna occidentalis growing in the botanical garden of the University of Lagos, Akoka, Nigeria, were investigated using standard plate count and biochemical techniques. Bacteria were the most predominant in the rhizosphere of both plants, followed by fungi, then actinomycetes. The culturable microbial population was at its maximum for depths 10 and 15 cm in M. sapientum var parasidiaca. In S. occidentalis, bacterial population was highest at 5cm, fungi at 10cm and actinomycetes at 15cm depth of the rhizosphere. Bacillus cereus had 100% distribution in the rhizosphere of both plants and Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis each had 75% distribution in both rhizospheres. Rhizosphere depth of 10 cm had 100% distribution of bacteria, and the least bacterial distribution was found at 20cm. Fungi were most distributed at 15cm rhizosphere of M. sapientum var parasidiaca and at 10 and 15 cm rhizosphere of S. occidentalis. Rhizopus stolonifer had 100% distribution and the highest % occurrence in the rhizosphere of both plants with Aspergillus niger having 100 and 75% distribution in the rhizosphere of M. sapientum and S. occidentalis respectively. Actinomycetes were most distributed at 10 cm (60 and 80% in rhizosphere of M. sapientum and S. occidentalis respectively). Streptomyces sp had the highest distribution in the rhizosphere of both plants and 58.33 and 55.17% occurrences in rhizosphere of M. sapientum and S. occidentalis respectively. Streptomyces alanosinicus and S. gancidicus were absent among the rhizosphere isolates of M. sapientum. Similarly, S. globosus and S. sampsonii were not found in the rhizosphere of S. occidentalis. The abundance of the microorganisms in these rhizospheres is typical of an environment with high species richness and functional diversity.
ABSTRACT
Members of lactic acid bacteria (LAB) are known probiotics and have been reported to have antimicrobial properties. Although various researchers have documented the isolation of these bacteria from fruits and vegetables; studies on LAB associated with lettuce; cucumber and cabbage are limited and non-existing in Nigeria. This study was designed to assess lettuce; cucumber and cabbage as potential sources of LAB and investigate the actions of their bacterial cell supernatants (BCS) on some pathogenic bacteria. Using standard microbiological methods; isolated LAB were identified to species level with API 50 CH kits (Biomerieux; France). Cell free supernatants (CFS) from de Man Rogosa Sharpe (MRS) broth cultures of the LAB strains were used to challenge Pseudomonas aeruginosa ATCC 27853; Enterococcus faecalis ATCC 29212; Escherichia coli ATCC 12900 and Proteus penneri ATCC 13315 by agar well diffusion method. The control consisted of the sterile MRS broth subjected to the same growth conditions as LAB broth cultures. A total of four lactic acid bacteria were isolated as follows: Pediococcus pentosaceus 2 from cucumber; Lactobacillus cellobiosus from cabbage; Lactobacillus salivarius and Lactobacillus plantarum 1 from lettuce. Pediococcus pentosaceus 2 and L. salivarius showed inhibitory effects on all the standard strains tested while L. plantarum 1 showed no inhibitory activity against E. faecalis and E. coli. Lactobacillus cellobiosus showed inhibition against all except P. penneri. Although; the molecular characterisation and probiotic potentials of these LAB strains are being investigated in an on-going study; we presumed these vegetables are prospective sources of the bacteria in Nigeria and therefore the need to extensively investigate the vegetables and other related vegetables becomes imperative