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Biotechnology

Year: 2005 | Volume: 4 | Issue: 2 | Page No.: 114-120
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Authors

S. Zamanian

G.H. Shahidi Bonjar

I. Saadoun

Keywords

Research Article

First Report of Antibacterial Properties of a New Strain of Streptomyces plicatus (Strain 101) Against Erwinia carotovora subsp. Carotovora from Iran

S. Zamanian, G.H. Shahidi Bonjar and I. Saadoun
This is the first report of antibacterial activity of Iranian actinomycetes isolates against Erwinia carotovora subsp. carotovora (Jones) Dye. E. carotovora subsp. carotovora is a soil born destructive plant pathogen with worldwide economical importance. Chemical measures have lost their attractiveness because of development of resistant strains of pathogens and due to undesirable effects on environment. Therefore, the studies on biological control of plant pathogens in soil have gained great importance worldwide. Actinomycetes, by virtue of their wide distribution, filamentous growth in soil, their ability to colonize the root surface and the rhizosphere, inhibitory effect on microorganisms and their ability to produce copious amounts of secondary metabolites especially antibiotics, role as a influential biological control agents have received special attentions. In order to obtain antibacterial antagonists from soil actinomycetes, a survey performed as follows. Soil samples taken from agricultural soils of Kerman. Serial dilutions provided and cultured in Casein Glycerin Agar (CGA). Over 110 isolates were screened among which one isolate showed high level of activity in Agar disk and Well diffusion methods against E. carotovora subsp. carotovora and identified as a new strain of Streptomyces plicatus (strain 101). This strain was propagated in submerged cultures and active crude was prepared upon which some biological characterization performed. High concentration of antibacterial agent was detected in 10th to 11th day in shake cultures. The active substance was water-soluble and insoluble in chloroform, hexan and dichloromethane. Minimal Inhibitory Concentration (MIC), by solving the crude extract in the dimethylsulfoxide plus methanol (v/v, 1:1) was determined as 5 mg mL-1. Longevity in vitro (LIV) of active crude of S. plicatus strain 101 against E. carotovora subsp. carotovora in soluble state determined about 30 days at room temperature. In thermal inactivation point studies, active crude retained activity up to 135°C. Antibacterial genes from this strain may be proper candidate for genetic engineering of plants for increased tolerance against the tested cosmopolitan bacterial pathogen.
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