Screening and Characterization of Biosurfactant-Producing Bacillus Species Isolated from Contaminated Soils in Makurdi Metropolis

Biosurfactants synthesized by microorganisms are chemically diverse and have gained interest industrially due to their surface and interfacial tensions-reducing activities. In this study Bacillus species from contaminated soils were screened and characterized for biosurfactant production. The study was carried out at the Microbiology Laboratory, Federal University of Agriculture Makurdi, Nigeria. The Bacillus species were isolated from kerosene shops, palm oil shops, nearby restaurants, mechanic workshops and abattoir effluents- contaminated soil samples collected from Makurdi metropolis. The Bacillus spp. were screened for biosurfactants production potentials using various screening methods (oil spreading, beta haemolysis, drop collapse and emulsification index). Specific primers were used to amplify the srfAA (surfactin gene) gene in the Bacillus isolates and the nucleotide sequences were determined at Inqaba Biotec, South Africa. The screening results were statistically analysed using analysis of variance (ANOVA) at 95 % confidence level. Isolate RT7(4)B exhibited the ability to produce biosurfactant, as well as the highest emulsification index (E24) of 73.25 % while isolate PO7(3)C gave the highest oil displacement of 6.77 mm. The supernatant obtained from isolate RT7(4)B showed reduction in surface tension of up to 30.26 mN/m. The isolates gave positive results for biosurfactant production when subjected to drop collapse and Beta haemolytic tests. The Polymerase chain reaction (PCR) results revealed amplifications of srfAA gene from 7 isolates. Based on these findings, the isolates used in this study can be utilized for biosurfactant production, and can also be useful for bioremediation and industrial biotechnology applications. Keywords: Biosurfactants; emulsification index; Bacillus; surface tension; Drop collaps

Single and mixed infection effects of Fusaruim oxysporum (Schlecht) Hansen & Synder and Meloidogyne javanica (Treub) Chitwood on the growth components of susceptible and resistant tomato plants

Single and mixed infection of Meloidogyne javanica and Fusarium oxysporum on growth of susceptible and resistant tomato plants were investigated in pot experiments. The experiments were arranged in completely randomised design with 5 replications. Pie-pan technique was used for nematode extraction and the fungus was obtained from root rhizosphere soil. Data were subjected to one-way ANOVA. Results showed that single and mixed infections significantly reduced some growth components of the susceptible tomato. However, combined effects were not significantly different from that inflicted by either of the pathogens. Gall rating indicated no significant differences among single and mixed infections, although successive inoculation where fungus preceded that by nematode significantly reduced number of galls. For resistant tomato, single and combined infections did not impact significantly on the growth parameters except for shoot length, root length and dry weight. Number of galls showed significant differences in this order of decreasing magnitude N or N+F or N+f, F+n and C at p ≤ 0.05. In both susceptible and resistant tomato, simultaneous infections caused the most reduction in the growth components and number of galls. That resistant tomato was not adversely impacted in single and combined infections underscores the need for its use in tomato production for improved yiel

Interaction between soybean mosaic potyvirus and Meloidogyne incognita infection

Infection of soybean (Glycine max (L.) Merrill) by soybean mosaic potyvirus (SMV) and root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, occurs wherever soybean is grown in Nigeria. The effect of concomitant infections of four soybean cultivars by SMV (isolate 10) and root-knot nematode (race 2) was investigated in greenhouse, experimental field and on-farm studies. Soybean mosaic potyvirus was introduced into soybean test plants by mechanical inoculation of homogenised crude extract from infected leaves suspension into a shallow trench around the base of test plants. In all four soybean cultivars, simultaneous or successive inoculation with both the nematode and the virus resulted in more severe symptoms and, therefore, reduced yield and yield components when compared with inoculations with each pathogen alone, although the difference was not much with plants inoculated with virus only. The results were more variable under experimental field and on-farm conditions than under more uniform greenhouse conditions. However, there was a significant interaction (P=0.05) between inoculation treatments and cultivars. Since multi-pathogen infections depressed yields more than single infections, more emphasis should be placed on evaluating or breeding for combined resistance to both pathogens in soybeans.L'infection du soja (Glycine max (l.) Merril) par le virus de la mosaque du soja (soybean mosaic potyvirus (SMV) et du nematode des racines, Meloidogyne incognita (Kofoid et white) Chitwood, a cours partout ou le soja est cultive au Nigeria. L'effet des infections de quatre cultivars du soja par SMV (isolate 10) et de nematodes des racines (race 2) etait introduit dans les plantes de soja par inoculation mecanique draits bruts homognes de feulles infestees, alors que lculation du nematode des racines etait realisee en versant une suspension dfs du nematode dans une tranchee peu profonde autour de la base des plant test. Pour les quatre cultivars de soja, lculation simultanee ou successive avec la fois le nematode et le virus a donne lieu des synptomes plus sevres et a par consequent entraine une baissse de rendement separement comparee aux inoculations des agents pathognes, bien que la difference nit pas sensible avec les plantes inoculees avec les seuls virus. Ces resultats entre cultivars etaient plus variables en champs experimentaux et en milieu reel que dans le serre ou les conditions sont plus uniformes. Cependant, il y avait une interaction (P=0.05) sensible entres les traitement dculation et de cultivars. Des lors que l'infection avec une multitude d'agents pathognes a occasione une baisse de rendement superieure a celle avec un seul pathogne, lent devrait etre mis sur l'evaluation ou la selection en vue d'une resistance combinee deux agents pathogenes du soja

HEAVY METAL CONTAMINATION OF YAMS PRODUCED IN BENUE STATE

Yam production play a vital role in the socio-economical scene of Benue State. This study seeks to determine the concentration of heavy metal in Yam tubers produced in Benue State. Two species of Yams Dioscorea rotundata and Dioscorea alata were selected as they are the most cultivated species in Benue state. Yams were sampled from nine sampling stations; three farming communities from Oturkpo, Ukum, and Tarka Local Government Areas (LGAs). A total number of 324 yam tubers were sampled for laboratory analyses of heavy metals (Arsenic (As), Cadmium (Cd), Chromium (Cr), and Lead (Pb), and residues of fertilizers (NPK, Urea, and Biuret impurities). The concentration of the heavy metals were analyzed using Atomic Absorption Spectrophotometry (AAS) 6800. The mean concentration of As, Cd, Cr, and Pb in the yams were 1.3887, 0.0126, 0.0452, and 0.0286 Mg/kg. The concentration of As, Cd, Cr, and Pb in Dioscorea alata were 2.7657, 0.0125, 0.03570, and 0.0251 while the concentration of the heavy metals in Dioscorea rotundata were 0.0136, 0.0129, 0.0550, and 0.0325  Mg/Kg respectively. Arsenic dominated al heavy metals analyzed in the yam varieties and the concentration of the heavy metals varied between the two sampled yam species. It was observed that the concentration of As, Cd, and Pb were greater than the Maximum Residual Limits (MRLs) of the World Health Organization (WHO) and Food and Agriculture Organization (FAO)