Polycyclic aromatic hydrocarbon-degrading bacteria from aviation fuel spill site at Ibeno, Nigeria.

Polycyclic aromatic hydrocarbon (PAH)-degrading bacteria were isolated from aviation fuel contaminated soil at Inua Eyet Ikot in Ibeno, Nigeria. PAH-degrading bacteria in the contaminated soil were isolated by enrichment culture technique. Isolates with high PAH degrading potential characterized by their extensive growth on PAH-supplemented minimal salt medium were screened for their naphthalene, phenanthrene and chrysene degradability. The screening medium which contained selected PAHs as the sole source of carbon and energy showed that Micrococcus varians AFS-2, Pseudomonas putida AFS-3 and Alcaligenes faecalis AFS-5 exhibited a concentration-dependent growth in all the PAH-compounds tested. There were visible changes in the color of growth medium suggesting the production of different metabolites. Their acclimation to different PAH substrates was also evident as A. faecalis AFS-5 isolated from chrysene grew well on other less complex aromatic compounds. The isolate exhibited best growth (0.44 OD(600)) when exposed to 10 ppm of chrysene for 5 days and could utilize up to 90 ppm of chrysene. This isolate and others with strong PAH-degrading potentials are recommended for bioremediation of PAHs in aviation fuel-contaminated sites in the tropics.

Fate of nitrogen-fixing bacteria in crude oil contaminated wetland ultisol.

The effect of crude oil on the growth of legumes (Calopogonium muconoides and Centrosema pubescens) and fate of nitrogen-fixing bacteria in wetland ultisol was investigated using standard cultural techniques. The results revealed observable effects of oil on soil physico-chemistry, plant growth and nodulation as well as on densities of heterotrophic, hydrocarbonoclastic and nitrogen fixing bacteria. The effects however varied with different levels (0.5%, 1%, 5%, 10%, 15% and 20%) of pollution. Ammonium and nitrate levels were high in the unpolluted soil but decreased with increase in pollution levels. Nitrite was not detected in contaminated soil probably due to the reduction in numbers of nitrogen fixers, from 5.26 ± 0.23 × l0(6)cfu/g in unpolluted soil to 9.0 ± 0.12 × 10(5) and 2.2 ± 0.08 × l0(5) cfu/g in soils with 5% and 20% levels of pollution respectively. The contaminated soil also exhibited gross reduction in the nodulation of legumes. A range of 13-57 nodules was observed in legumes from polluted soil against 476 nodules recorded for plants cultured on unpolluted soil. The heterogeneity of the microbial loads between oil-polluted and unpolluted soil were statistically significant (p < 0.05, ANOVA). Positive significant relationships were observed between the levels of hydrocarbons and the densities of heterotrophic bacteria (r = 0.91) and that of hydrocarbon utilizing bacteria (r = 0.86). On the other hand, relationships between the densities of nitrogen fixing bacteria and total hydrocarbons content was negative (r = -0.30) while positive relationships were recorded between the densities of different microbial groups and treatment periods except at 15% and 20% pollution levels. The LSD tests revealed highly significant differences (p < 0.001) in the physiological groups of soil microorganisms at all levels of pollution. The results imply that crude oil seriously affects rhizosphere microbial growth in legumes. Among the bacterial species isolated, Clostridium pasteurianum, Bacillus polymyxa and Pseudomonas aeruginosa exhibited greater ability to degrade hydrocarbons than Azotobacter sp, Klebsiella pneumoniae and Derxia gummusa while Nitrosomonas and Nitrobacter had the least degradability. A continuous monitoring of the environment is advocated to prevent extinction of nitrogen-fixing bacteria and total loss of soil fertility attributable to petroleum hydrocarbon contamination in the Niger Delta ultisol.

Heavy metal burdens in patches of asphyxiated swamp areas within the Qua Iboe estuary mangrove ecosystem.

This study examined the burden of Zn, Cu, Ni, Pb, Cr and V in patches of asphyxiated mangrove swamp areas within Qua Iboe Estuary mangrove ecosystem by sediments and surface water analysis; in order to establish natural background levels of these metals and to assess anthropogenic influences on them. The analysis shows that the mean concentrations (mg/kg, dw) of Zn, Cu, Ni, Pb, Cr and V in sediments from asphyxiated and healthy mangrove ecosystems of Qua Iboe vary from 36.3-179.4, 29.2-43.2, 3.6-37.4, 39.6-93.8, 0.15-0.53 and 2.9-9.3, with the former exhibiting higher metal accumulating potential. Although heavy metal concentrations in surface water of the asphyxiated swamp were low, their accumulative effect is significant. The concentrations of Cu and Pb in surface water of this ecosystem exceeded the water quality criteria while Ni and Cr were under the maximum concentration for drinking water quality and protection of aquatic life. The values of pollution load index (PLI), which are generally greater than unity, show that the sediments and the surface water from the asphyxiated mangrove ecosystem were polluted with heavy metals, thus suggesting anthropogenic activities as a possible source of these metals. The mean concentrations of Zn, Ni and Pb exceeded the effects range-low (ERL), indicating that there may be some ecotoxicological risk to organisms living in asphyxiated mangrove sediments.

Heat resistance of dermatophyte's conidiospores from athletes kits stored in Nigerian University Sport's Center.

The incidence and heat resistance of conidiospores produced by dermatophytes isolated from athlete's kits (canvasses, stockings and spike shoes) stored in Nigerian University Sport's Centre were investigated. Epidermophyton floccosum, Microsporum oudouinii, Microsporum canis, Trichophyton concentricum, Trichophyton mentagrophytes and Trichophyton rubrum were isolated and their incidence on the athlete's kits varied with the species and type of kits. Among the isolates T. mentagrophytes, T. rubrum and E. floccosum with 25%, 23% and 20% prevalence rates respectively, were the most common isolates, and are often associated with tinea pedis (athletes foot). Canvasses with the highest incidence of dermatophytes (25 out of 34 fungal isolates) were the most contaminated kits and could serve as effective articles for the transmission of tinea pedis among athletes in Nigeria. The common etiological agents screened, produced asexual spores (conidiospores) that exhibited high resistance to heat treatment at 80 degrees C. Of the three isolates, E. floccosum, with a decimal reduction time (D-value) of D80 = 4.4 min was the most resistant followed by T. mentagrophytes with D80 = 4.0 min and then T. rubrum with D80 = 3.2 min. The spores elimination pattern indicates that increasing the heating duration would decrease the decimal reduction time and possibly denature the fungal propagules but may damage the skin during treatment with hot water compresses. The findings have shown that the use of hot water compresses is palliative but heat treatment especially vapour-heat treatment offers adequate preventive measures if applied for periodic treatment of contaminated kits. However, determining the correct condition for effective decontamination will require detailed understanding of the heat resistance of fungal spores. Otherwise treatment of kits with detergent and chaotropic agent such as urea and guanidinium salt is preferred to heat treatment.

Growth, keratinolytic proteinase activity and thermotolerance of dermatophytes associated with alopecia in Uyo, Nigeria.

Mycological research was conducted on the mycelial growth, keratinolytic proteinase activity and thermotolerance ofdermatophytes associated with alopecia patients in Uyo, Nigeria. The results revealed that Microsporum sp. - AP1, Epidermophyton sp. - AP2, Trichophyton rubrum - AP4, Trichophyton mentagrophytes - AP5 and a yeast Candida albicans - AP3 isolated exhibited variable growth and keratinase activity at different temperatures. Microsporum sp. - AP1 and T. mentagrophytes - AP5 survived heat treatment at 90 degrees C but exhibited best mycelial growth at 30 degrees C (with 53.41 mg/50 ml biomass dry weight) and 40 degrees C (with 61.32 mg/50 ml biomass dry weight) respectively, after incubation for 2 weeks. Trichophyton rubrum - AP4 and Epidermophyton sp. - AP2 could not survive heat treatment at 90 degrees C but grew better at 40 degrees C (with 38.52 mg/50 ml biomass dry weight) and 30 degrees C (with 48.32 mg/50 ml biomass dry weight) respectively, over the same incubation period, while C. albicans - AP3 grew better at 30 degrees C with 38.7 mg/50 ml biomass dry weight after 2 weeks, but failed to survive at 70 degrees C. All the isolates except Candida albicans - AP3 survived at 80 degrees C and exhibited great potential to elaborate keratinolytic enzymes, with T. mentagrophytes demonstrating the best potential at 30 degrees C and 40 degrees C. Higher temperatures tended to reduce keratinolytic activities and there were significant (P < 0.05) relationships between biomass weight and enzyme productivities of all the isolates except T. mentagrophytes. This indicates that in some dermatophytes keratinolytic proteinase activity is not a function of cell multiplicity. This plus the high thermostability of the enzymes are important attributes in the consideration of preventive and therapeutic methods against dermatophytes in the tropics.

Chromatium species: an emerging bioindicator of crude oil pollution of tidal mud flats in the Niger Delta mangrove ecosystem, Nigeria.

Establishing microbiological indices for the monitoring of environmental decay by crude oil pollution in the Niger Delta region has been a major concern of our current researches. Chromatium species, a purple, Gram positive pleomorphic, motile, microaerophlic sulfur bacterium offers a good potential for use in the assessment of the short term effects of oil pollution of tidal mud flats in the Niger Delta mangrove ecosystem. Its response to the November 22, 2003 spillage at the Qua Iboe Estuary and the adjoining Cross River Estuary was investigated. Our results have revealed that the sulphur bacterium is easily identified and widely distributed in the epipellic sediment of the mangrove ecosystem but very sensitive to hydrocarbon pollution. The bacterium was readily detected in the tidal mud flats containing as much as 2.0 mg kg(-1) but not detected in sediment with THC level of 3.65 mg kg(-1) and above. It is thus, suggestive that the threshold and lethal limits of effect of hydrocarbons against the sulfur bacterium lies between 2.04 and 3.65 mg kg(-1). These imply that in any case of crude oil pollution that Chromatium is not detected during monitoring the THC levels of the sediment may have been raised to a level close to or above 3.65 mg kg(-1). Statistical analysis of the relationship between THC level and density of Chromatium in sediment revealed a significant (p < 0.05) negative relationship (r = -0.85) in Qua Iboe mangrove ecosystem as against an insignificant (p > 0.05) relationship (r = -0.41) recorded for the Cross River mangrove ecosystem which served as the control. The result indicates that oil pollution affect the homeostatic status of Chromatium in tidal mud flats despite its even distribution (R2 = 71.4%). The finding though not definitive may contribute to the hierarchical process of oil pollution assessment in the Niger Delta region of Nigeria. However, its effective utilization will require not only the development of a selective medium for enumeration and isolation of the bacterium but also the establishment of a defined dose-response relationship under controlled conditions which requires further research.

Productivity and distribution of epipellic microalgae along salinity gradients in mangrove swamp of the Qua Iboe Estuary (Nigeria).

Based on spatial variation in tidal mud salinity, direct gradient analysis procedures were adopted to relate the productivity and distribution of epipellic microalgae along salinity gradients in mangrove swamp of the Qua Iboe Estuary. Variations in mud salinities were due to distance from the coast, tidal incursions and freshwater input. The dilution effect of fresh water input from rainfall, urban runoff and associated freshwater creeks was most severe during the rainy season month of July, with much lower salinity levels recorded, in comparison to higher salinity values, recorded for same sampling locations during the drier month of December. In the dry season, all the microalgae species but Closterium (a genus of soft, green algae) and Oscillatoria (a cyanobacterium) species encountered in the tidal mud flats showed statistically significant negative correlations with salinity, while most microalgae species excluding Oscillatoria and Closterium species were positively correlated with the same factor during the wet season. Four Ecological Groups of microalgae, were established in the dry season month of December as against two Ecological Groups in the wet season month of July. However no microalgae species was found to occur on the highest values of mud salinity and there were overlapping range of occurrences and ecological optima for most species along the gradients.

Studies on mould growth and biomass production using waste banana peel.

Hyphomycetous (Aspergillus fumigatus) and Phycomycetous (Mucor hiemalis) moulds were cultivated in vitro at room temperature (28 + 20 degrees C) to examined their growth and biomass production on waste banana peel agar (BPA) and broth (BPB) using commercial malt extract agar (MEA) and broth (MEB) as control. The moulds grew comparatively well on banana peel substrates. No significant difference (p > 0.05) in radial growth rates was observed between moulds cultivated on PBA and MEA, although growth rates on MEA were slightly better. Slight variations in sizes of asexual spores and reproductive hyphae were also observed between moulds grown on MEA and BPA. Smaller conidia and sporangiospores, and shorter aerial hyphae (conidiophores and sporangiophores) were noticed in moulds grown on BPA than on MEA. The biomass weight of the test moulds obtained after one month of incubation with BPB were only about 1.8 mg and 1.4 mg less than values recorded for A. fumigatus and M. hiemalis respectively, grown on MEB. The impressive performance of the moulds on banana peel substrate may be attributed to the rich nutrient (particularly the crude protein 7.8% and crude fat 11.6% contents) composition of banana peels. The value of this agricultural waste can therefore be increased by its use not only in the manufacture of mycological medium but also in the production of valuable microfungal biomass which is rich in protein and fatty acids.

Bioamendment of petroleum contaminated ultisol: effect on oil content, heavy metals and pH of tropical soil.

The effect of organic amendments on the oil content, heavy metals concentration and pH of petroleum contaminated sandy loam ultisol obtained from Rumuekpe oil field in Emohua Local Government Area of Rivers State, Nigeria was determined. Petroleum contaminated soils were treated with wood ash, compost and sawdust. The addition of organic amendments resulted in a significant (at 95% probability level) decrease in oil content by 92% for composting, 81% for soil treated with sawdust and 58% for soil with ash supplementation, over 6 months. The effect of treatments on the iron(Fe), copper(Cu) and lead(Pb) concentration was significant at P < 0.001. The remediation also affected the pH of soil. This initial pH of 5.6 was depressed by the application of compost and sawdust supplements respectively to a final pH of 5.2 and 5.3. On the other hand, amending the soil with wood ash raised the pH from 5.6 to 6.2. Increased acidity caused a decrease in the heavy metals concentration in the contaminated soil. Soil treatment with compost generally gave the best remediation results, followed by sawdust and then ash. Adjusting the pH of oil contaminated soil to high acidic levels may promote the availability and migration of heavy metals in remediated soils and not necessarily the rate of oil mineralization.