Journal of Tropical Microbiology and Biotechnology

Identification of toxin genes encoding Cyt proteins from standard and Argentine strains of Bacillus thuringiensis

2013-07-18T04:48:53+00:00

Polymerase chain reaction-restriction fragment length polymorphism methods for identification of cyt subclasses from Bacillus thuringiensis were established. Eight of 68 standard and ten of 107 Argentine B. thuringiensis strains harbor at least one cyt gene. The combination of cyt1Aa/cyt2Ba genes was identified in four standard and in ten native strains, whereas the cyt1Ba, cyt2Aa and cyt2Bb genes alone and the cyt1Ab/cyt2Bc genes together were found in four different standard strains respectively. The cyt2Ba genes from three B. thuringiensis svar israelensis strains and two Argentine B. thuringiensis strains were cloned, sequenced and designated as cyt2Ba10 to cyt2Ba14 respectively. These results suggest that these methods are relevant tools for identification of toxin genes encoding Cyt proteins in B. thuringiensis.

Keywords: Bacillus thuringiensis, cyt1, cyt2, PCR-RFLP

J. Trop. Microbiol. Biotechnol. 8: 3-8

Response of pigeon pea genotypes to different races of Fusarium udum and the mode of gene action responsible for disease inheritance

2013-07-18T04:48:53+00:00

To develop high yielding Fusarium wilt resistant varieties, it is essential to identify new sources of resistance that can withstand multiple races of the pathogen. The aim of this study was to identify [Fusarium udum (L.) Millsp.] races occurring in the study fields, determine reaction of pigeon pea hybrids to the different isolates and establish the mode of gene action responsible for Fusarium wilt inheritance. Field and pot experiments were conducted during 2009 and 2010. A root-dip inoculation and transplantation technique in pots and sowing in a wilt-sick field were used for studying the reactions of 54 pigeon pea genotypes to F. udum isolates. Field evaluation was done in the infested plot in a 9 x 6 alpha lattice design with two replications. Purification of the isolates on potato dextrose agar identified three isolates and were designated as ISO-A, ISO-B, and ISO-C. The isolates produced whitish to light pink or orange mycelia. Purple was predominant on the substrate, but whitish to light pink were also identified. Pot inoculation trials with the three isolates identified seven genotypes (ICPB2043, ICP12012, ICP13092, ICPA2039xICP13092, ICPA2043xICP12012, ICPA2043xICP13092, and ICPA2043xICP9135) resistant to all the isolates. Under field evaluation, seven genotypes (ICPA2039xICP13092, ICPA2039xAsha, ICPA2043xICP12012, ICPA2043xICP13092, ICPA2043xICEAP557, ICPB2043, and Maruti) were moderately resistant. The cytoplasmic male sterile (A) line, A2043, showed resistance to the three isolates. The resistant hybrid, ICPA2943xICP12012 had the highest negative SCA that was highly significant for all the isolates in the field.

Keywords: Fusarium udum, pigeon pea genotypes, pigeon pea isolates, Kenya, wilt-sick field

J. Trop. Microbiol. Biotechnol. 8:9-19 9

Isolation and characterization of bacterial isolates from Lake Magadi

2013-07-18T04:48:53+00:00

Microorganisms from soda lakes have attracted attention as a possible source of novel enzymes and metabolites for use in industrial applications. Isolation and characterization of bacteria from Kenyan soda lakes has been done mainly in Lakes Elmenteita, Bogoria and Nakuru. Only a few studies have been documented on Lake Magadi, a hyper saline lake with up to 30% salinity levels. This study sought to isolate alkaliphilic bacteria from Lake Magadi that could produce novel enzymes and antimicrobial compounds, and document for further exploitation. Nearly 55 isolates were obtained using different media prepared with filter-sterilised water from the lake, which were characterized and screened for production of extracellular enzymes and/or antimicrobial compounds. Bacteria retrieved grew well at pH ranging from 5 – 10, temperature range of 25 – 50 oC and sodium chloride range of 0- 30 %. The isolates produced amylases, lipases, proteases and esterases and exhibited a range of inhibitory effects on various test organisms. Analysis of partial sequences of 16S rRNA genes using Blast showed that 80 % of the isolates were affiliated to the genus Bacillus, while 20% were affiliated to members of Gammaproteobacteria. Five (5) isolates showed identity of 95 - 97 % similarity with the previously known sequences and could represent novel bacterial species, while 4 isolates had a sequence identity of 80 - 93% similarity to known organisms, and could represent novel genera. This study demonstrated that the extreme environment of Lake Magadi harbors novel alkaliphilic bacteria with potential for production of enzymes and antimicrobial compounds.

Keywords: Soda lakes, Alkaliphiles, extreme environment, enzymes and antimicrobial compounds

J. Trop. Microbiol. Biotechnol. 8:17-25 17