Plant diseases accounts for huge losses in agriculture. To ensure food security and sustainability, an agricultural yield must be improved to meet the growing world population. Due to growing awareness of the effect of pesticides and herbicides on human health and the environment, an alternative safe method of controlling phytopathogens has become a subject of intense research. Biological control of plant diseases is the use of living organisms to suppress or inhibit plant pathogens. Microbiological control agents (MBCAs) employ microorganisms to protect crops from destruction by phytopathogens through different modes of action. They may act by direct interaction with the pathogens through hyperparasitism. Indirect antagonistic interaction with the pathogen through induction of host resistance and priming is another mode of attack by MBCAs. Competition for nutrients and space is another important indirect mode of attack by which MBCAs suppress the growth of pathogens through nutrient deprivation. The MBCAs can also interact with the plant through secretion of antibiotics or antimicrobial secondary metabolites with inhibitory effect against the pathogens. A clear understanding of the mode of action of MBCAs is vital to achieving a successful biocontrol operation as well as improving the biocontrol process that is devoid of risks to humans and the environment. Such improvement could be achieved through the use of microbial consortia to enhance the stability and efficiency of the biocontrol process. Further studies on aspects of mass production and formulation to produce more effective, stable, safer and cost effective MBCAs are needed.
The extensive use of pesticides is one of the major causes of pollution of soil and water environments. The current method for removing such contaminants from the environment through biodegradation has been shown to be more effective than any other method. Three pesticide degrading bacteria were isolated and identified through cultural and biochemical tests as strains of Pseudomonas aeruginosa, Serretia marcescens and Klebsiella oxytoca. Their growth in mineral salt medium supplemented with 20mg/l of Chlorpyrifos was monitored at optical density of 600nm. The result showed that Pseudomonas aeruginosa had maximum growth in ten days, while Serretia marcescens and Klebsiella oxytoca recorded highest growth after six days of incubation. HPLC analysis of the residual Chlorpyrifos after 14 days incubation showed that Pseudomonas aeruginosa was able to degrade 60% of the pesticide; Klebsiella oxytoca degraded 54%, while Serretia marcescens had 53% reduction of the pesticide concentration in the mineral salt medium. The results of this research indicated that the isolated bacteria can be used for bioremediation of Chlorpyrifos contaminated soil and water ecosystems.
Well water is a source of drinking water for many rural as well as sub-urban dwellers but the pollution of this water by bacteriological and chemical contaminants is of public health concern. Hence this study was aimed at accessing the bacteriological quality and physicochemical parameters of well waters located in Emene-Enugu, Nigeria. Water samples were aseptically drawn from ten different wells in Emene-Enugu. Physicochemical parameters such as temperature, pH, turbidity and electrical conductivity were determined using standard methods. Total and fecal coliform counts were also determined using the membrane filtration method. The isolates were also identified using cultural and biochemical tests. Pearson’s correlation was used to determine the relationship between the parameters. Temperature of the well waters ranged from 31.5±0.11 to 33.7±0.11oC while the pH ranged from 6.20±0.01 to 7.40±0.01. Turbidity and conductivity also ranged from 25±0.05 to 150±0.06 NTU and 21±0.58 to 163±0.12µS/cm respectively. Total and fecal coliform counts ranged from 0 to 179±2.31 cfu/100ml and 0 to 58±0.58 cfu/100ml respectively. Bacteria identification revealed the presence of Enterobacter aerogenes, Salmonella enterica, Enterococcus faecalis, Proteus vulgaris, Escherichia coli, Klebsiella pneumonia and Citrobacter freundii, in the water samples. Turbidity was significantly correlated with temperature, pH and fecal coliform (p = 0.000; r = 0.693, p = 0.000; r = -0.679 and p = 0.000; r = -0.655) respectively. These isolates are potential human pathogens, thus the well waters used in this study are not fit for human consumption and should be properly treated and monitored before domestic use.
Waste engine oil (WEO) constitutes a potential hazard to humans, animals and vegetation. Studies on the effects of metals on organic pollutant biodegradation demonstrate that metals have the potential to inhibit pollutant biodegradation. Fungi were isolated from soil samples contaminated with WEO using vapour phase transfer method. The ability of the isolates to utilize WEO was assessed using gravimetric method. The impact of Zn and Pb and the effect of pH (5.5, 7.0 and 8.5) on WEO biodegradation by the pure and consortium culture of the isolates were determined. A total of 8 fungal isolates were obtained in this study. 4 that showed high hydrocarbonoclastic potentials were confirmed as Candida tropicalis, Rhodosporidium toruloides, Fusarium oxysporium and Aspergillus clavatus using 18S r RNA gene sequence. C. tropicalis and A. clavatus exhibited the highest extent of biodegradation of WEO and were therefore selected for further studies. Although there was significant (P<0.05) increase in inhibition of WEO degradation at high concentration of the heavy metals with increase in pH, low concentration of the metals stimulated the degradation of used engine oil. Highest stimulation of 10.1% and 14.2% was recorded in the presence of 1.0 mg/L Zn and Pb at pH 5.5, with the consortium culture and A. clavatus, respectively. The results showed that the pure and consortium culture of the isolates (C. tropicalis and A. clavatus) have promising potential for effective bioremediation of waste engine oil polluted soil cocontaminated with low levels of Zn, and Pb at pH 5.5.
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