boybiss998
Junior Member
Bacillus subtilis and Bacillus pumilus were isolated from soil and screened for the production of antibiotics by plate assay and then cultured in shake flask fermentation at 30o C for further studies. Identification of antibiotics was done by paper chromatography. Bacitracin was found to be produced by both the strains against Micrococcus luteus (ATCC# 10240), whereas; Staphylococcus aureus (ATCC# 6538) proved to be resistant to Bacitracin produced by Bacillus pumilus. The maximum production of Bacitracin from B. subtilis and B. pumilus against Staphylococcus aureus and Micrococcus luteus at different pH (6-9), incubation time (0-144 hours) and glucose concentration (1-5%) was checked by agar diffusion assay as detected by the size of zones of inhibition. Maximum zones of inhibition were observed at pH 8, 5% glucose and after 24 hours of incubation at 30o C against Staphylococcus aureus and Micrococcus luteus
. Introduction
The word “antibiotic” is derived from Greek term antibiosis, which literally means “against life”. It can be purified from microbial fermentation and modified chemically or enzymatically for either chemical use or for fundamental studies (Robbers et al., 1996; De Mondena et al., 1993). The antibiotics are widely distributed in the nature, where they play an important role in regulating the microbial population of soil, water, sewage and compost. Of the several hundred naturally produced antibiotics that have been purified, only a few have been sufficiently non-toxic to be of use in medical practice. Those that are currently of greatest use have been derived from a relatively small group of microorganisms belonging to the genera Penicillium, Streptomyces, Cephalosporium, Micromonospora and Bacillus (Zinsser et al., 1988). More than 5000 different antibiotics have been isolated from cultures of bacteria, fungi and plant cells, 60% of them are contributed by the genus Streptomyces (Todar, 2002; Claus & Blackwill, 1989). In pharmaceutical industry, several peptide antibiotics of importance are produced by Bacillus species such as bacitracin, polymyxin, gramicidin, tyrocidine, subtilin, bacilysin etc. Bacilli are rod-shaped, Gram-positive, sporulating, aerobes or facultative anaerobes. Most bacilli are saprophytes. Each bacterium creates only one spore, which is resistant to heat, cold, radiation, desiccation, and disinfectants. Bacilli exhibit an array of physiologic abilities that allow them to live in a wide range of habitats, including many extreme habitats such as desert sands, hot springs, and Arctic soils. Species in the genus Bacillus can be thermophilic, psychrophilic, acidophilic, alkaliphilic, halotolerant or halophilic and are capable at growing at pH values, temperatures, and salt concentrations where few other organisms can survive
Most of the peptide antibiotics produced by bacilli are active, against gram-positive bacteria; however, compounds such as polymyxin, colistin and circulin exhibit activity almost exclusively upon gram-negative bacteria, whereas bacillomycin, mycobacillin and fungistatin are effective against molds and yeasts (Katz & Demain, 1977). Berdy (1974) reported the production of 167 peptide antibiotics from Bacillus subtilis and Bacillus brevis. Of this total, 66 different peptide antibiotics are elaborated by strains of Bacillus subtilis and 23 are products of Bacillus brevis
. Materials and Methods
Isolation of bacitracin producing microorganisms: Soil samples were collected from rhizosbhere and checked for the presence of antibiotic producing microorganisms. Susceptible test organisms that is; Micrococcus luteus (ATCC# 10240) and Staphylococcus aureus (ATCC# 6538) was isolated on nutrient agar plates. Soil was sprinkled on the lawn of M. luteus and S. auerus. Plates were incubated at 30o C for 24 hours. After incubation the plates were checked for the appearance of zones of inhibition around the colonies of microorganisms.
Identification of Bacillus species: Isolated strains were identified on the basis of their morphological and biochemical characteristics according to Bergey’s Manual of Determinative Bacteriology (Buchanan & Gibbons, 1974).
. Introduction
The word “antibiotic” is derived from Greek term antibiosis, which literally means “against life”. It can be purified from microbial fermentation and modified chemically or enzymatically for either chemical use or for fundamental studies (Robbers et al., 1996; De Mondena et al., 1993). The antibiotics are widely distributed in the nature, where they play an important role in regulating the microbial population of soil, water, sewage and compost. Of the several hundred naturally produced antibiotics that have been purified, only a few have been sufficiently non-toxic to be of use in medical practice. Those that are currently of greatest use have been derived from a relatively small group of microorganisms belonging to the genera Penicillium, Streptomyces, Cephalosporium, Micromonospora and Bacillus (Zinsser et al., 1988). More than 5000 different antibiotics have been isolated from cultures of bacteria, fungi and plant cells, 60% of them are contributed by the genus Streptomyces (Todar, 2002; Claus & Blackwill, 1989). In pharmaceutical industry, several peptide antibiotics of importance are produced by Bacillus species such as bacitracin, polymyxin, gramicidin, tyrocidine, subtilin, bacilysin etc. Bacilli are rod-shaped, Gram-positive, sporulating, aerobes or facultative anaerobes. Most bacilli are saprophytes. Each bacterium creates only one spore, which is resistant to heat, cold, radiation, desiccation, and disinfectants. Bacilli exhibit an array of physiologic abilities that allow them to live in a wide range of habitats, including many extreme habitats such as desert sands, hot springs, and Arctic soils. Species in the genus Bacillus can be thermophilic, psychrophilic, acidophilic, alkaliphilic, halotolerant or halophilic and are capable at growing at pH values, temperatures, and salt concentrations where few other organisms can survive
Most of the peptide antibiotics produced by bacilli are active, against gram-positive bacteria; however, compounds such as polymyxin, colistin and circulin exhibit activity almost exclusively upon gram-negative bacteria, whereas bacillomycin, mycobacillin and fungistatin are effective against molds and yeasts (Katz & Demain, 1977). Berdy (1974) reported the production of 167 peptide antibiotics from Bacillus subtilis and Bacillus brevis. Of this total, 66 different peptide antibiotics are elaborated by strains of Bacillus subtilis and 23 are products of Bacillus brevis
. Materials and Methods
Isolation of bacitracin producing microorganisms: Soil samples were collected from rhizosbhere and checked for the presence of antibiotic producing microorganisms. Susceptible test organisms that is; Micrococcus luteus (ATCC# 10240) and Staphylococcus aureus (ATCC# 6538) was isolated on nutrient agar plates. Soil was sprinkled on the lawn of M. luteus and S. auerus. Plates were incubated at 30o C for 24 hours. After incubation the plates were checked for the appearance of zones of inhibition around the colonies of microorganisms.
Identification of Bacillus species: Isolated strains were identified on the basis of their morphological and biochemical characteristics according to Bergey’s Manual of Determinative Bacteriology (Buchanan & Gibbons, 1974).
