Characteristics and antimicrobial activity of Bacillus subtilis strains isolated from soil

Abstract

Antagonistic Bacillus strains were isolated from soil and analyzed for the purpose of determining whether they could be used as natural biological agents. Primary in vitro screening for antagonism of the isolates was performed against five phytopathogenic mould fungi. Strains TS 01 and ZR 02 exhibited the most pronounced inhibitory effects. They were identified as Bacillus subtilis on the basis of their morphological, cultural and physiology-biochemical properties as well as their hierarchical cluster analysis conducted by means of computer program SPSS. The antimicrobial activity of the strains from cultural medium and sterile filtrate were determined in vitro against a great number of predominantly phytopathogenic fungi and bacteria. TS 01 and ZR 02 strains exhibited very broad and at the same time degree varying antibiotic spectra of activities against both Gram-positive and Gram-negative microorganisms. Many of them were tested against sensitivity to the antimicrobial action of B. subtilis for the very first time. B. subtilis TS 01 and ZR 02 showed highest antifungal activity (sterile zone in diameter over 37 mm) against Alternaria solani, Botrytis cinerea, Monilia linhartiana 869, Phytophthora cryptogea 759/1 and Rhizoctonia sp. The most sensitive bacterial species were found to be Pseudomonas syringae pv. tomato Ro and Xanthomonas campestris with sterile zones 48.0 and 50.0 mm in diameter, respectively. The latter draws a conclusion that the isolated and identified Bacillus subtilis strains are promising natural biocontrol agents and should be further studied and tested for control of numerous plant diseases.

Activity of extracellular compounds of Pseudomonas sp. against Xanthomonas axonopodis in vitro and bacterial leaf blight in eucalyptus

“…Many authors reported the use of antagonistic microorganisms such as fungi, rhizobacteria and especially bacteria of genus Bacillus and Pseudomonas as biocontrol agents for plant diseases (Shoda, 2000;Byrne et al, 2005;Lemessa & Zeller, 2007;Todorova & Kozhuharova, 2010). However, there are few reports about the use of microorganisms or secondary metabolic compounds in the control of X. axonopodis of eucalyptus.…”

Bacillus subtilis LBF02 as Biocontrol Agent Against Leaf Spot Diseases Caused by Cercospora lactucae-sativae in Lettuce

“…The LBF02 isolated exhibited the most pronounced antagonism against C. lactucae-sativae when compared with the control. Todorova & Kozhuharova (2010) report that previous studies of the antagonistic Bacillus subtilis strains TS 01 and ZR 02, which were isolated from soil, reveal that they showed the highest antifungal activity against Alternaria solani, Botrytis cinerea, Monilia linhartiana, Phytophthora cryptogea and Rhizoctonia sp. Favorable results were also found by Korsten & Jager (1995) …”

“…The test of the ability of the study bacteria LBF02 to isolate for physiological and biochemical characterization was carried out as described in Bergey's Manual of Systematic Bacteriology (Holt et al, 1984;Todorova & Kozhuharova, 2010;Zheng et al, 2007). The following sources of carbon were used: glucose, lactose, maltose, fructose, sucrose, mannitol, sodium citrate and urease.…”

“…Based on the biochemical and morphological tests according to Bergey's Manual of Systematic Bacteriology (Holt et al, 1984;Todorova & Kozhuharova, 2010;Zheng et al, 2007), the detailed physiological characteristics of LBF02 were investigated and compared with Bacillus subtilis, as shown in Table 1. The strain LBF02 consisted of spore-forming, Gram-positive rod shaped, bacteria colonies which were convex colonies with wrinkled surface, circular, white-cream, entire and opaque on nutrient agar.…”

“…In the year 2004, due to an attack of just the Cercospora longissima comm losses of up to 68% were reported in the specific conditions (Gomes et al, 2004). All these antagonistic bacteria that have been isolated from the soil surrounding the plants and from the plant surfaces (Weller, 1988;Kim et al, 1997;Sindhu et al, 2002;Todorova & Kozhuharova, 2010) are active under the general mechanism of competitive exclusion or reduction of growth by other microorganisms, which is the interference process of the pathogens. Moreover, the antagonistic bacteria manufacture a diverse range of secondary metabolites due to enzymatic activity and therapeutics due to various mechanisms of secretion and are capable of catalyzing various biochemical reactions with novel enzymes of lytic enzymes, siderophores and antibiotics (Das et al, 2006).…”