Inhibition of dehydrogenase activity in pathogenic bacteria isolates by aqueous extracts of Musa paradisiaca (Var Sapientum)

Inhibition of dehydrogenase activity in pathogenic bacteria isolates by aqueous extract from the unripe fruit peels (called the bark) and leaves of Musa paradisiaca var sapientum were investigated via dehydrogenase assay using 2,3,5-triphenyl tetrazolium chloride (TTC) as the electron acceptor. Pure cultures of Staphylococcus and Pseudomonas species were exposed to varied concentrations of theextract [0 – 2000 ìg/ml]. The extracts exhibited concentration dependent response against the tested organisms. Dehydrogenase activities (mg Formazan/mg cell dry weight/h) in the Gram-positiveStaphylococcus sp. and Gram-negative Pseudomonas sp. were 1.125 ± 0.056 and 0.740 ± 0.040, respectively, and were progressively inhibited in the pure cultures. Threshold inhibitory concentrations(IC50) of M. paradisiaca bark extract were 143.5 and 183.1 ìg/ml against Staphylococcus and Pseudomonas species, respectively, while the threshold inhibitory concentrations (IC50) of M. paradisiaca leaf extract were 401.2 and 594.6 ìg/ml, respectively. The IC100 of the leaf extract against Staphylococcus and Pseudomonas species were 1850 and 2000 ìg/ml respectively, while the bark could not completely inhibit the organisms at the tested concentrations. The bark and leaves of M. paradisiaca may be an available source of raw material for the production of chemotherapeutic agents against pathogenic bacteria

In vitro effects of metals and pesticides on dehydrogenase activity in microbial community of cowpea (Vigna unguiculata) rhizoplane

Effects of heavy metals and pesticides on cowpea (Vigna unquiculata) rhizoplane microbial community  were assessed in vitro via dehydrogenase activity. The microbial community was exposed to various concentrations of heavy metals and pesticides in a nutrient broth-glucose-2,3,5-triphenyl chloride (TTC) medium. At 0.2 mM, iron and cadmium stimulated the dehydrogenase activity of the microbialcommunity. For all the metal ions, there was progressive inhibition with each successive increase in the concentration of metal ion, reaching near 100% at 0.6, 0.8, 1.2, 0.12 and 12 mM for cobalt, cadmium,iron, mercury and nickel, respectively. Between 0.2 and 0.4 mM, zinc sharply inhibited dehydrogenase activity and at concentration above 0.4 mm, inhibition of dehydrogenase activity became lesspronounced. The order of toxicity is Hg2+ > Co2+ > Cd2+ > Zn2+ > Fe2+ > Ni2+. The herbicides Cotrazine (Atrazine 80W) and Northrin®10EC stimulated dehydrogenase activity of the microbial community at 0.2% and inhibited it at higher concentrations. The median inhibitory concentrations (IC50s) of Cotrazine(Atrazine 80W) and Northrin®10EC were 0.552 ± 0.028 and 0.593 ± 0.051%, respectively. The dehydrogenase activity varied significantly (p < 0.05) with the type and concentrations of metals orpesticides. The result indicates that the heavy metals and pesticides are potentially toxic to V. unquiculata root surface microorganisms. In soil, this toxicity may affect nitrogen fixation processes and by extrapolation affect crop yield

Prevalence and risk factors of malaria among children in southern highland Rwanda

<p>Abstract</p> <p>Background</p> <p>Increased control has produced remarkable reductions of malaria in some parts of sub-Saharan Africa, including Rwanda. In the southern highlands, near the district capital of Butare (altitude, 1,768 m), a combined community-and facility-based survey on <it>Plasmodium </it>infection was conducted early in 2010.</p> <p>Methods</p> <p>A total of 749 children below five years of age were examined including 545 randomly selected from 24 villages, 103 attending the health centre in charge, and 101 at the referral district hospital. Clinical, parasitological, haematological, and socio-economic data were collected.</p> <p>Results</p> <p><it>Plasmodium falciparum </it>infection (mean multiplicity, 2.08) was identified by microscopy and PCR in 11.7% and 16.7%, respectively; 5.5% of the children had malaria. PCR-based <it>P. falciparum </it>prevalence ranged between 0 and 38.5% in the villages, and was 21.4% in the health centre, and 14.9% in the hospital. Independent predictors of infection included increasing age, low mid-upper arm circumference, absence of several household assets, reported recent intake of artemether-lumefantrine, and chloroquine in plasma, measured by ELISA. Self-reported bed net use (58%) reduced infection only in univariate analysis. In the communities, most infections were seemingly asymptomatic but anaemia was observed in 82% and 28% of children with and without parasitaemia, respectively, the effect increasing with parasite density, and significant also for submicroscopic infections.</p> <p>Conclusions</p> <p><it>Plasmodium falciparum </it>infection in the highlands surrounding Butare, Rwanda, is seen in one out of six children under five years of age. The abundance of seemingly asymptomatic infections in the community forms a reservoir for transmission in this epidemic-prone area. Risk factors suggestive of low socio-economic status and insufficient effectiveness of self-reported bed net use refer to areas of improvable intervention.</p

Physiological stress response of sediment bacteria to interacting effects of petroleum refinery effluent

In vitro effects of the refinery effluent on physiological response of sediment bacterial strains was evaluated via reduction of 2, 3, 5-triphenyl tetrazolium chloride by dehydrogenase activity of the test organisms. Results obtained showed a range of responses by the organisms. The physiological responses of the bacterial strains were concentration-depended. Dehydrogenase activity in pure cultures of Pseudomonas sp. SD1, Bacillus sp. SD3 and Corynebacterium sp. SD4 were stimulated at effluent concentration of 12.0% (v/v), while at 25.0 %(v/v), the effluent stimulated dehydrogenase activity in Aeromonas sp. SD2. In all the cultures, dehydrogenase activity was progressively inhibited at concentrations greater than 25% (v/v). The median inhibitory concentrations of the effluent (IC20) ranged from 29.076&#177;1.05 to 42.836&#177;2.14 and (IC50) ranged from 49.905&#177;1.16 to 58.465&#177;2.28% (v/v) among the organisms respectively. Aeromonas sp. SD2 seemed to tolerate the toxicity of the effluent more than Pseudomonas sp.SD1 at IC20 and IC50. The result of the interactive effects showed that the organisms could be good candidates for bioremediation of petroleum effluents polluted media as IC50 values obtained showed little high tolerance to toxic effect of petroleum refinery raw effluent by the sediment bacterial strains isolated from effluent affected Okrika River. Keywords: Petroleum, refinery effluent, bacteria, dehydrogenase activity, bioremediation International Journal of Natural and Applied Sciences, 7(1): 22 - 28, 201

Tolerance of phenol-utilizing bacteria to heavy metals in the Aba River sediments

Bacteria strains were isolated from sediment of tropical fresh water River that receives industrial discharges and were screened for utilization of phenol as the sole carbon and energy. Pseudomonas, Arthrobacter and Staphylococcus species were able to utilize 10.0 mM of phenol while Escherichia and Bacillus species were unable to utilize more than 5.0 mM of phenol. Metal-resistant bacteria were selected and minimal inhibitory concentrations (MIC) of heavy metals for each isolate were determined using tube dilution method. On the bases of MICs, all the strains showed tolerance to Zn, Cu, Cd, Pb, Ni, Co, Cr and Hg. The bacterial strains exhibited varying degrees of tolerance depending on the metal type. Copper and Nickel were best tolerated metals. Mercury and Zinc were the most toxic metals for all bacteria.Keywords: Heavy metal, phenol-utilizing bacteria, Aba River, sediment International Journal of Natural and Applied Sciences, 6(1): 55-61, 201

Influence of ph and inoculum size on phenol utilization by bacterial strains isolated from oil refinery effluent

The influence of pH and inoculum size on phenol utilization by bacterial isolates from oil refinery effluent was investigated. The substrate used for the assessment was phenol, which formed a model substrate for the experiment. Phenol was progressively degraded at pH range of 6.3 to 8.0. Maximum phenol degradation by Bacillus sp. RBD1 and Corynebacterium sp. RBD2 was obtained at pH value of 7.1. Conversely, utilization of phenol at pH 5.5 was significantly high for both organisms. Phenol was degraded at every cell density (inoculum size) tested with the two organisms but phenol degradation rate increased with increasing inoculum size. Cultures of Bacillus sp. RBD1 and Corynebacterium sp.RBD2 with the lowest cell densities exhibited highest specific rate of utilization of phenol. The results obtained indicated lower phenol utilization rate per colony forming unit at higher cell density. It was also found that pH 6.3 to 8.0 was found to be optimal for phenol degradation by the test organisms.Keywords: Phenol, pH, refinery wastewater, bacteria, inoculum size, biodegradation International Journal of Natural and Applied Sciences, 7(1): 8 - 15, 2011 ISSN: 0794 &#8211; 471