Study of Antibacterial properties of Actinomycetes isolates from hospital waste
Research Students:
A.B
Supervisor:
Upendra Thapa Shrestha
Assistant professor
1. Introduction
Actinomycetes comprise an extensive and diverse group of Gram-positive, aerobic, mycelial bacteria with high G+C nucleotide content (>55%), and play an important ecological role in soil cycle. The name of the group actinomycetes is derived from the first described anaerobic species Actinomyces bovis that causes actinomycosis, the ‘ray-fungus disease’ of cattle. They were originally considered to be intermediate group between bacteria and fungi but are now recognized as prokaryotic microorganisms (Kuster 1968).
The majority of Actinomycetes are free living, saprophytic bacteria found widely distributed in soil, water and colonizing plants. Actinomycetes population has been identified as one of the major group of soil population (Kuster 1968), which may vary with the soil type. They belong to the order Actinomycetales (Superkingdom: Bacteria, Phylum: Firmicutes, Class: Actinobacteria, Subclass: Actinobacteridae). According to Bergey's Manual Actinomycetes are divided into eight diverse families: Actinomycetaceae, Mycobacteriaceae, Actinoplanaceae, Frankiaceae, Dermatophilaceae, Nocardiaceae, Streptomycetaceae, Micromonosporaceae (Holt, 1989) and they comprise 63 genera (Nisbet and Fox, 1991). Based on 16s rRNA classification system they have recently been grouped in ten suborders: Actinomycineae, Corynebacterineae, Frankineae, Glycomycineae, Micrococineae, Micromonosporineae, Propionibacterineae, Pseudonocardineae, Streptomycineae and a large member of Streptomyces are still remained to be grouped (www.ncbi.nlm.nih.gov). Actinomycetes have characteristic biological aspects such as mycelial forms of growth that accumulates in sporulation and the ability to form a wide variety of secondary metabolites including most of the antibiotics.
One of the major groups in actinomycetes is Streptomyces. Streptomyces contains 69-78 mol% of G+C. Substrate and aerial mycelium is highly branched. Substrate hyphae are 0.5-1.0 µm in diameter. In the colony ages aerial mycelia develop into chain of spores (conidia) by the formation of crosswalls in the multinucleated aerial filaments. Conidial wall are convoluted projection which together with the shape and the arrangement of the spore-bearing structure are characteristic of each species of Streptomyces (Anderson et al., 2001). It produces several antibiotics including of aminoglycosides, anthracyclins, glycopeptides, b-lactams, macrolides, nucleosides, peptides, polyenes, polyethers and tetracyclines (Sahin and Ugur, 2003).
Thus investigators turn towards Streptomyces and also other genera of actinomycetes such as Nocardia, Micromonospora, Thermoactinomycetes etc. for isolation of novel antibiotics. No doubt soil is the natural habitat of most of the microorganisms where vast array of bacteria, actinomycetes, fungi and other organisms exist and provided with suitable growth condition and ability to proliferate. Thus most actinomycetes contributing to antibiotic production are screened from soil (Williams and Khan, 1974).
Our prime focus is to find out the novel antibiotic with broad-spectrum antimicrobial activity from Actinomyecetes isolates of hospital waste.
2. Background
In, RLABB, The first work on the diversity of actinomycestes was started by Singh, D. and Agrawal, V.P. (2002). The research on actinomycetes form
3. Objectives
1. To collect and isolate actinomycetes from the hospital waste samples.
2. To purify and identify the actinomycetes isolates.
3. To screen the actinomycetes isolates for antibiotic production by primary and secondary screening methods.
4. Hypotheses
It is hypothesized that Actinomycetes from hospital waste may have developed broad spectrum antibiotic producing properties during their continuous interaction with different types of clinically important bacteria in their natural niche. Therefore the actinomycetes isolates from such habitat may be of great importance in medical field.
5. Methodology
5.1. Isolation and Purification of Actinomycetes
Hospital waste samples will be collected from different hospital waste dumping sites in plastic pouches, sealed and transferred to Research Laboratory of Universal Science College where entire research work will be carried out. Isolation of actinomycetes will be performed by dilution plate technique using Starch-Casein Agar (Singh and Agrawal, 2002 & 2003). Actinomycetes on the plates will be identified as colored, dried, rough, with irregular/regular margin; generally convex colony as described by Williams and Cross (1971). Streak plate method will be used to purify cultures of actinomycetes (Williams and Cross, 1971, Singh and Agrawal 2002; Agrawal 2003). After isolation of the pure colonies, each different cology will be identified on the basis on their colonial morphology, colour of hyphae, color of aerial mycelium and microscopy. Then they will be individually plated on single same agar medium for short time preservation.
5.2. Morphological and Biochemical characterization
Morphological examination of the actinomycetes will be done by using cellophane tape and cover slip-buried methods (Williams and Cross, 1971; Singh and Agrawal 2002; Singh and Agrawal 2003). The mycelium structure, color and arrangement of conidiophores and arthrospore on the mycelium will be examined under oil immersion (1000X). The observed structure will be compared with Bergay’s manual of Determinative Bacteriology, Ninth edition (2000) for identification Streptomyces spp. Different biochemical tests will be performed to characterize the Streptomyces spp. The tests generally used are gelatin hydrolysis, starch hydrolysis, urea- hydrolysis, acid production from different sugars utilization tests, resistance to NaCl, temperature tolerance test, hydrogen sulphide production test, motility test, triple sugar iron (TSI) agar test, citrate utilization test, indole test, methyl red test, voges-proskauer (Acetoin Production) test, catalase test, oxidase test (Holt 1989; Singh and Agrawal 2002; Singh and Agrawal 2003).
5.3. Screening of Actinomycetes for antimicrobial activity
5.3.1 Primary screening:
Primary screening of pure isolates will be determined by perpendicular streak method on Muller Hinton agar (MHA). In vitro screening of isolates for antagonism: MHA on Nutrient Agar (NA) plates will be prepared and inoculated with Actinomycetes isolate by a single streak of inoculum in the center of the petridish. After 4 days of incubation at 28 °C the plates were seeded with test organisms (Bacillus subtilis, Staphylococcus aureus, Enterobacter aerogens, Escherichia coli, Klebsiella species, Proteus species, Pseudomonas species, Salmonella typhi and Shigella species) by a single streak at a 90° angle to Actinomycetes strains. The microbial interactions were analyzed by the determination of the size of the inhibition zone.
5.3.2 Secondary screening:
Secondary screening is performed by agar well method against the standard test organism. Fresh and pure culture of each strain from the primary screening will be inoculated in starch casein broth and incubated at accordingly for 7 days in water bath shaker. The visible pellets, clumps or aggregates and turbidity in the broth, will confirm growth of the organism in the flask. Contents of flasks will be filtered through Whatman no.1 filter paper. The filtrate will be used for the determination of antimicrobial activity against the standard test organisms by agar well method.
6. Expected Outcomes
Being majority of antibiotics producing bacteria are Actinomycetes (mainly Streptomyces spp.) our research work will select different actinomycetes producing only broad-spectrum antibiotics effective against the clinically important bacteria. The actinomycetes will be screened by both primary and secondary screening methods. Any of potent strain from such sample will be further studied.
7. References
Holt JG 1989 Bergey's manual of systematic bacteriology, vol 4, ed. S.T. Williams and M.E. Sharpe,
Kuster HJ, (1968) Uber die Bildung Von Huminstoffen durch Streptomyceten. Landwirtsch. Forsch
Nisbet LJ and Fox FM (1991) The importance of microbial biodiversity to biotechnology, In, The biodiversity of microorganisms and invertebrates: its role in sustainable Agriculture, ed.D.L. Hawksworth, 224-229, CAB International.
Pandey B, Ghimire P and Agrawal VP (2004) Studies on Antibacterial Activity of Soil from Khumbu Region of
Sahin N and Ugur A (2003) Investigation of the Antimicribial Activity of some Streptomyces isolates. Turk J Biol 27: 79-84.
Singh D and Agrawal VP (2002) Microbial Biodiversity of Mount Everest Region, a paper presented in International Seminar on Mountains -
Singh D and Agrawal VP (2003) Diversity of Actinomycetes of Lobuche in Mount Everest I Proceedings of International Seminar on Mountains –
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