Effects of Bacillus thuringiensis CRY1A(c) d-endotoxin on growth, nodulation and productivity of beans [Phaseolus vulgaris (L.) and siratro (Macroptilium atropurpureum DC.)]

The recent introduction of Bt maize and Bt cotton transgenic crops into Africa has raised concerns on their potential short and long-term ecological effects on the environment. The effects of Bacillus thuringiensis (Bt) Cry1A(c) d-endotoxin on the growth, nodulation and productivity of two leguminous plants grown in clay soil were evaluated. Bt Cry1A(c) d-endotoxin from a local B. thuringiensis isolate (ICIPE L1-2) active against Chilo partellus (Swinhoe) was used. Beans (Phaseolus vulgaris L.) and Siratro (Macroptilium atropurpureum DC.) seedlings were grown in pots treated with Bt Cry1A(c) dendotoxin solution (100 ìg/ml). Control experiments were treated with water. The plants were maintained in the greenhouse until nodulation (8 weeks) and maturity (14 weeks) stages when sampling was done for measurements of morphological, productivity and nodulation traits. Nodulation was observed in both plants species. Nitrogen content in treatments for both bean and siratro plants, withand without Bt-toxin not were significantly different. Leaf area, plant dry weight, number of pods per plants and number of seeds per pod observed in treatments with and without Bt-toxin for both bean and siratro plants were also not significantly different. This shows that Bt Cry1A(c) delta-endotoxin does not interfere with the host plant growth, nodulation and productivity in clay soil. Findings will provide researchers with data to design more robust experiments and will inform the decisions of diversestakeholders regarding the safety of transgenic crops

Molecular typing and antibiotic sysceptibility patterns of enteropathogenic and shigatoxin producing Escherichia coli isolated from food handlers in three areas of Kenya

Objectives: To determine the aetiology, epidemiology and sanitary factors of carriage of enteropathogenic Escherichia coli (EPEC) and Shiga-toxin producing E. coli (STEC) in food-handlers working in tourist hotels in three popular tourist destinations in Kenya.Design: Cross sectional laboratory based study.Setting: Three tourist destinations of Nairobi, Malindi and Diani in Kenya.Subjects: Food handlers who were working in hotels frequented by tourists in the three study sites.Results: Overall, during the period of April 2003 to May 2004, a total of 1399 food handlers stool samples were collected and analysed. EPEC expressing the eaeA gene and STEC expressing the stx2 gene were detected in 11/1399 (0.8%) and 2/1399 (0.1%) of the study subjects respectively. The mean age of the subjects from whom EPEC and STEC were isolated was similar (32.6 years) to those from whom no EPEC and STEC were isolated (32.5 years). Prior use of antibiotics, water source and toilet types were not significantly associated with the isolation of EPEC and STEC (p>0.05). There were 11 resistance patterns with six isolates (6/13, 46.2%) showing multidrug resistance. High prevalence of resistance was observed to co-trimoxazole (55.6%), chloramphenicol (33.3%), ampicillin (22.2%) and tetracycline (22.2%). High concentrations of antibiotics were required to achieve MlC90 for tetracycline, (>64 mg ml-1) and ampicillin (>256 mg ml-1). Cluster analysis of the Pulse Field Gel Electrophoresis profiles revealed that the EPEC and STEC isolates belonged to two main genotypes with 11 distinct DNA fragment profiles.Conclusion: This is the first report in Africa on the isolation of STEC from food handlers working in tourist hotels. These food handlers who carry the STEC and EPEC could potentially infect tourists and other people through food or water contamination in the hotel settings and thus our findings are of great public health importance

Bacterial diversity in the intestinal tract of the funguscultivating termite Macrotermes michaelseni (Sjöstedt)

Microorganisms in the intestinal tracts of termites play a crucial role in the nutritional physiology of termites. The bacterial diversity in the fungus-cultivating Macrotermes michaelseni was examined usingboth molecular and culture dependent methods. Total DNA was extracted from the gut of the termite and 16S rRNA genes were amplified using bacterial specific primers. Representatives from forty-one (41) RFLP patterns from a total of one hundred and two (102) clones were sequenced. Most of the clones were affiliated with 3 main groups of the domain Bacteria: Cytophaga-Flexibacter-Bacteriodes(73), Proteobacteria (13), and the low G+C content Gram-positive bacteria (9). Two RFLPs related to planctomycetes, but deeper branching than known members of the phylum, were detected. In addition, 1 and 2 RFLPs represented the spirochetes and TM7-OP11 groups, respectively. In studies using culture dependent techniques, most of the isolates obtained belonged to the Gram-positive bacteriawith a high G+C content. However, only one of the clones represented Gram-positive bacteria with High G+C content. These results show a high bacterial diversity in the intestinal microbiota of M. michaelseni, which continues to escape cultivation. As is the case in other termites many of the clones represent previously uncultured bacteria. The fact that most of the clones clustered with clones from Macrotermes gilvus provides further support for the hypothesis that microorganisms in intestinal tracts of termites have co-evolved with their hosts

(Per)chlorate reduction by an acetogenic bacterium, Sporomusa sp., isolated from an underground gas storage

A mesophilic bacterium, strain An4, was isolated from an underground gas storage reservoir with methanol as substrate and perchlorate as electron acceptor. Cells were Gram-negative, spore-forming, straight to curved rods, 0.5–0.8 μm in diameter, and 2–8 μm in length, growing as single cells or in pairs. The cells grew optimally at 37°C, and the pH optimum was around 7. Strain An4 converted various alcohols, organic acids, fructose, acetoin, and H2/CO2 to acetate, usually as the only product. Succinate was decarboxylated to propionate. The isolate was able to respire with (per)chlorate, nitrate, and CO2. The G+C content of the DNA was 42.6 mol%. Based on the 16S rRNA gene sequence analysis, strain An4 was most closely related to Sporomusa ovata (98% similarity). The bacterium reduced perchlorate and chlorate completely to chloride. Key enzymes, perchlorate reductase and chlorite dismutase, were detected in cell-free extracts

A short Communication: Distribution of heterotrophic bacteria in the sediments in the mangrove swamp at Gazi Bay, Kenya

In the first ever study of microorganisms in an East African mangrove swamp, the number of aerobic heterotrophic bacteria in the mangrove swamp sediment was investigated and found to range from 7.44 × 106 to 4.70 × 108 cfu/g dry wt, (cfu = colony forming units; g dry wt = gram dry weight). The anaerobic heterotrophic bacteria ranged from 7.45 × 106 to 1.82 × 108 cfu/g dry wt. There was no significant difference between the Avicennia marina, Ceriops tagal and Rhizophora mucronata sediments with respect to the number of aerobic and anaerobic bacteria. The exercise was conducted between October and February and generally lower numbers of bacteria were recorded between mid December and February. Key words: Mangrove swamps, heterotrophic bacteria Journal of Tropical Microbiology Vol.1(1) 2002: 41-4

Isolation, Characterization And Identification Of Enterobacteriaceae From Well Water In Juja Town In Kenya

Water for docmestic use is increasingly becoming a scarce resource forcing communities to resort to underground water sources. However, increasing wells and boreholes are facing threats of pullution from sewage. Water samples were collected from 12 different wells in Juja town, Kenya using pre-sterilized 100 ml plastic bottles. Sampling was done in May 2004 during the long rains and in September 2004 during the dry season. All the water samples had total coliform counts >1100 per 100 ml of water. The Enterobacteriaceae isolated from the wells were from the following genera: Escherichia, Enterobacter, Citrobacter, Proteus, Edwardsiella, Erwinia, Kluyvera, Klebsiella, Salmonella, Shigella, Serratia, Rahnella, Cedecea, Morganella, and Yersinia. Bacteria detected but not belonging to Enterobacteriaceae included the genera Vibrio, Acinetobacter, and Chromobacterium. Indiscriminate refuse disposals as well as the location of septic tanks, soak away pits and pit latrines in proximity to the wells could be the most probable cause of the overall high number of coliforms in the wells. Water treatment through chlorination or boiling was shown to reduce the microbial load to zero. Therefore it is recommended that water from the shallow wells be treated through chlorination or boiling before it can be used for domestic purposes.Keywords: shallow wells, coliforms, fecal pollution, water treatmen

Isolation and characterization of bacterial isolates from Lake Magadi

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 compoundsJ. Trop. Microbiol. Biotechnol. 8:17-25 1

Effects of Bacillus thurungiensis Cry1A(c) &#948-endotoxin on diversity of Legume Nodulating Bacteria (LNB) and nitrogen fixation in Clay soil

Bt technology alleviates many problems associated with the use of chemical pesticides, contributes to increased grain yields and a reduced need for insecticidal sprays. However, the potential impacts of Bt crops on the environment remain a topic of debate worldwide, calling for the assessment of Bt crops on the environment. In the current study, the effect of Bacilllus  thuringiensis (Bt) Cry1A(c) d-endotoxin on the diversity of legume nodulating bacteria (LNB) and nitrogen fixation in clay soil was evaluated. Bt Cry1A(c) d-endotoxin from a  local B. thuringiensis isolate (ICIPE L1-2) active against Chilo partellus (Swinhoe) was used.  Beans  (Phaseolus  vulgaris  L.)  and  Siratro  (Macroptilium  atropurpureum DC.)  seedlings were  grown  in  pots  treated with Bt Cry1A(c)  d-endotoxin  solution  (100  μg/ml). Control  experiments were  treated with water. The  plants were maintained  in  the greenhouse until nodulation  (8 weeks)  stage when  sampling was done. LNB were  isolated  from  the  root  nodules. Restriction fragment  length polymorphism  (RFLP) assessed  the diversity of  the LNB  species. Soil  samples  in hungate  tubes were  treated with Bt Cry1A(c)  d-endotoxin  solution  (100  μg/ml)  and  the  control  sample  sprayed with  equally  volume  of  distilled water. Subsequently,  acetylene  reduction  assays  were  performed  over  a  60  hour  period.  The  results  showed  that  Bt  Cry1A(c)  d-endotoxin had no effect on nitrogen  fixation  rates by  free  living  soil microorganisms. However, RFLP data  showed a  slightly higher  diversity  of  LNB  in  the  control  samples  than  the  test  samples,  indicating  that  Bt  Cry1A(c)  d-endotoxin  (100  μg/ml) reduced or modified the number of LNB in the rhizosphere.Key words: Bacillus thuringiensis, Bt Cry1A(c) δ-endotoxin, Macroptilium atropurpureum (DC.), RFLP