Properties, environmental fate and biodegradation of carbazole

The last two decades had witnessed extensive investigation on bacterial degradation of carbazole, an N-heterocyclic aromatic hydrocarbon. Specifically, previous studies have reported the primary importance of angular dioxygenation, a novel type of oxygenation reaction, which facilitates mineralization of carbazole to intermediates of the TCA cycle. Proteobacteria and Actinobacteria are the predominant bacterial phyla implicated in this novel mode of dioxygenation, while anthranilic acid and catechol are the signature metabolites. Several studies have elucidated the degradative genes involved, the diversity of the car gene clusters and the unique organization of the car gene clusters in marine carbazole degraders. However, there is paucity of information regarding the environmental fate as well as industrial and medical importance of carbazole and its derivatives. In this review, attempt is made to harness this information to present a comprehensive outlook that not only focuses on carbazole biodegradation pathways, but also on its environmental fate as well as medical and industrial importance of carbazole and its derivatives

Cassava Wastewater and Solid Waste Leachate as Cyanogenic Substrates for the Growth of Nitrile and Linamarin-Utilizing Bacteria

The direct discharge of wastewaters containing cyanogenic compounds poses severe health hazards, hence this study aimed to establish the biodegradative potential of nitrile and linamarin utilizing bacterial strains in the degradation of cyanogens in cassava wastewaters (CWW) and solid waste leachates (SWL). Glutaronitrile-utilizing bacterial strains (Bacillus sp. strain WOD8 KX774193 and Corynebacterium sp. strains WOIS2 KX774194) were isolated from solid waste leachates while linamarin-utilizing bacteria strains (Bacillus pumilus strain WOB3 KX774195 and Bacillus pumilus strain WOB7 KX774196) were isolated from cassava wastewaters. They were identified on the basis of morphological and biochemical characteristics, microscopic and 16S rRNA gene sequencing. Microbial growth assessment coupled with pH changes were performed under aerobic batch conditions. Growth was evaluated at intervals (2 days) by the intensity of turbidity (O.D. 600 nm) in CWW and SWL media. The doubling times of strains WOD8 and WOIS2 when grown on CWW and SWL (without supplementing mineral salts medium) were 12.83 and 10.83 d (specific growth rate, µ: 0.054 and 0.064 d-1) and 20.38 and 17.77 d (µ: 0.034 and 0.039 d-1) respectively. Also, strains WOD8 and WOIS2 grew on supplemented CWW and SWL with doubling times of 10.04 and 9.9 d (µ: 0.069 and 0.070 d-1) and 16.12 and 16.12 d (µ: 0.043 and 0.043 d-1) respectively. Similarly, the doubling times of strains WOB3 and WOB7 when grown on CWW and SWL (without supplementing mineral salts medium) were 8.25 and 7.53 d (µ: 0.084 and 0.092 d-1) and 8.66 and 9.90 d (µ: 0.080 and 0.070 d-1) respectively. Whereas, the same strains had doubling times of 6.30 and 5.78 (µ: 0.11 and 0.12 d-1) and 6.30 and 9.24 (µ: 0.11 and 0.075 d-1) respectively when grown on supplemented CWW and SWL. It would appear that CWW has the highest potential as a natural growth substrate than SWL, and its use for biomass production may contribute to a reduction in the overall environmental impact generated by discarding cyanogenic residues

Effects of cadmium perturbation on the microbial community structure and heavy metal resistome of a tropical agricultural soil

The effects of cadmium (Cd) contamination on the microbial community structure, soil physicochemistry and heavy metal resistome of a tropical agricultural soil were evaluated in field-moist soil microcosms. A Cd-contaminated agricultural soil (SL5) and an untreated control (SL4) were compared over a period of 5 weeks. Analysis of the physicochemical properties and heavy metals content of the two microcosms revealed a statistically significant decrease in value of the soil physicochemical parameters (P < 0.05) and concentration of heavy metals (Cd, Pb, Cr, Zn, Fe, Cu, Se) content of the agricultural soil in SL5 microcosm. Illumina shotgun sequencing of the DNA extracted from the two microcosms showed the predominance of the phyla, classes, genera and species of Proteobacteria (37.38%), Actinobacteria (35.02%), Prevotella (6.93%), and Conexibacter woesei (8.93%) in SL4, and Proteobacteria (50.50%), Alphaproteobacteria (22.28%), Methylobacterium (9.14%), and Methylobacterium radiotolerans (12,80%) in SL5, respectively. Statistically significant (P < 0.05) difference between the metagenomes was observed at genus and species delineations. Functional annotation of the two metagenomes revealed diverse heavy metal resistome for the uptake, transport, efflux and detoxification of various heavy metals. It also revealed the exclusive detection in SL5 metagenome of members of RND (resistance nodulation division) protein czcCBA efflux system (czcA, czrA, czrB), CDF (cation diffusion facilitator) transporters (czcD), and genes for enzymes that protect the microbial cells against cadmium stress (sodA, sodB, ahpC). The results obtained in this study showed that Cd contamination significantly affects the soil microbial community structure and function, modifies the heavy metal resistome, alters the soil physicochemistry and results in massive loss of some autochthonous members of the community not adapted to the Cd stress

Assessment of the State of Herbal Medicines Research and Development in Nigeria

Purpose: To examine the state of herbal medicines research and development (R&D) outputs in universities, research institutes and pharmaceutical manufacturing firms in Nigeria. Methods: Questionnaires were administered to core researchers in the above-mentioned research organizations using purposive and convenient sampling technique. The questionnaire elicited vital information on researcher's area of specialization, academic qualifications, state of research facilities and approach to herbal medicines R&D by the organization. Data were analyzed using appropriate statistical tools. Results: The study revealed that the researchers were highly qualified individuals who specialized in eight distinct areas. Research facilities were in varying degrees of deterioration. Major R&D activities were incremental or modification of products/process (58 %), continuous improvement of R&D programs (23 %), radical process/product development (20 %), and creative (11 %) and duplicative (7 %) efforts. Strategies to enhance herbal medicine R&D were increased funding (36.3 %), training of researchers (28.1 %), improvement in R&D infrastructure (18.6 %) and fostering public-private partnership (17 %). Conclusion: Herbal medicines R#38;D is not fully developed in Nigeria due to a myriad of fundamental challenges facing the key players

Degradation of aviation fuel by microorganisms isolated from tropical polluted soils

The degradation of aviation fuel was observed in soil samples from a polluted site at the aviation fuel depot, Lagos Airport, Nigeria. The percentage of occurrence of bacterial aviation fuel–utilizers were less than 1.0% of the heterotrophic populations, while the fungal-degraders were between 2.547-16.053%. There were no significant statistical differences for both the bacteria and fungi estimations among the soil samples. Enrichment of soil samples with aviation fuel resulted in the isolation of five bacteria (Pseudomonas aeruginosa, Micrococcus luteus, Corynebacterium sp., Flavobacterium rigense, Bacillus subtilis), three yeasts (Rhodotorula sp., Candida tropicalis, Saccharomyces sp.) and two molds (Aspergillus niger, Penicillium sp.). Utilization of the substrate by bacteria and yeast isolates resulted in an increase in population density and subsequent decrease in pH value and residual aviation fuel concentration. Over 90% of the n-alkane fraction of the aviation fuel supplied at 0.5% v v-1 concentration was degraded in 14 days by Pseudomonas aeruginosa, Micrococcus luteus and Corynebacterium sp. There were differential growth responses by the strains to dodecane, benzene, toluene and naphthalene, while growth was not supported by hexane and cyclohexane. Thus, enrichment with of soil contaminated with aviation fuel led to the isolation of competent hydrocarbon degraders

Microbial communities in sediments of Lagos lagoon, Nigeria: elucidation of community structure and potential impacts of contamination by municipal and industrial wastes

Estuarine sediments are significant repositories of anthropogenic contaminants, and thus knowledge of the impacts of pollution upon microbial communities in these environments is important to understand potential effects on estuaries as a whole. The Lagos lagoon (Nigeria) is one of Africa’s largest estuarine ecosystems, and is impacted by hydrocarbon pollutants and other industrial and municipal wastes. The goal of this study was to elucidate microbial community structure in Lagos lagoon sediments to identify groups that may be adversely affected by pollution, and those that may serve as degraders of environmental contaminants, especially polycyclic aromatic hydrocarbons (PAHs). Sediment samples were collected from sites that ranged in types and levels of anthropogenic impacts. The sediments were characterized for a range of physicochemical properties, and microbial community structure was determined by Illumina sequencing of the 16S rRNA genes. Microbial diversity (species richness and evenness) in the Apapa and Eledu sediments was reduced compared to that of the Ofin site, and communities of both of the former two were dominated by a single operational taxonomic unit (OTU) assigned to the family Helicobacteraceae (Epsilonproteobacteria). In the Ofin community, Epsilonproteobacteria were minor constituents, while the major groups were Cyanobacteria, Bacteroidetes, and Firmicutes, which were all minor in the Apapa and Eledu sediments. Sediment oxygen demand (SOD), a broad indicator of contamination, was identified by multivariate analyses as strongly correlated with variation in alpha diversity. Environmental variables that explained beta diversity patterns included SOD, as well as levels of naphthalene, acenaphthylene, cobalt, cadmium, total organic matter, or nitrate. Of 582 OTU identified, abundance of 167 was significantly correlated (false discovery rate q≤ 0.05) to environmental variables. The largest group of OTU correlated with PAH levels were PAH/hydrocarbon-degrading genera of the Oceanospirillales order (Gammaproteobacteria), which were most abundant in the hydrocarbon-contaminated Apapa sediment. Similar Oceanospirillales taxa are responsive to marine oil spills and thus may present a unifying theme in marine microbiology as bacteria adapted for degradation of high hydrocarbon loads, and may represent a potential means for intrinsic remediation in the case of the Lagos lagoon sediments