Influence of pH, temperature and nutrient addition on the degradation of atrazine by Nocardioides spp. isolated from agricultural soil in Nigeria.

Aims: To effectively exploit the atrazine degrading capabilities of Nocardioides spp. isolated from agricultural soil samples in Nigeria and ascertain the effect of pH, temperature and nutrient addition on the degradation process. Methodology and results: Isolates were cultivated on atrazine mineral salts medium at a temperature range of 4 °C - 45 °C and a pH range of 3-10. An optimum atrazine degrading activity was observed in the isolates between temperatures of 25 °C and 37 °C and between pH 5 and 8. Different carbon sources (glycerine, glucose, chitin, cellulose and sodium citrate) and nitrogen sources (urea, biuret, cyanuric acid, potassium nitrate and ammonium chloride) were also added to the medium. The addition of carbon and nitrogen sources did not increase degradation rates although urea and glycerine repressed the degradation ability of the isolates. Statistical analyses of variance at P < 0.05 showed no significant differences in the growth and degradation rates by both bacterial isolates under these conditions. Conclusion, significance and impact study: Atrazine degradation by Nocardioides spp. is pH and temperature dependent, and requires no additional sources of carbon and nitrogen. Hence, its use in bioremediation of atrazine contaminated agricultural soil should be explored

Metal biouptake by actively growing cells of metal-tolerant bacterial strains

Metal uptake potentials of Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia CA96Co, Rhodococcus sp. AL03Ni, and Corynebacterium kutscheri FL108Hg were studied to determine their competence in detoxification of toxic metals during growth. Metabolism-dependent metal biouptake of the bacteria revealed appreciable uptake of the metals (57–61, 10–30, 23–60, and 10–16 mg g dw−1 of Ni2+, Cr6+, Co2+, and Cd2+, respectively) from medium, after initial drop in pH, without lag phase. The bacteria exhibited 95–100 % removal efficiency for the metals from aqueous medium as 21 (±0.8)–84 (±2.0) concentration factors of the metals were transported into the bacterial systems. Passive adsorption onto the cell surfaces occurred within 2-h contact, and afterwards, there was continuous accumulation for 12 days. Biosorption data of the bacteria were only fitted into Langmuir isotherm model when strains AL96Co, CA207Ni, and AL03Ni interacted with Ni2+, achieving maximum uptake of 9.87, 2.72, and 2.69 mg g dw−1, respectively. This study established that the actively growing bacterial strains displayed, at least, 97.0 % (±1.5) continuous active removals of metals upon adsorption. The bacteria would be good candidates for designing bioreactor useful in the detoxification campaign of heavy metal-polluted systems

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

Grappling with Bioeconomy Research and Discourse in Nigeria – Mixed Method to the Rescue

Very little is known about public understanding, awareness, and perception of bioeconomy in Nigeria where its adoption is scant. Addressing this problem, we adopted a mixed method research design study to investigate the level of understanding, perception, and awareness of bioeconomy and its products among 550 Lagos residents’, 500 survey respondents and 50 focus group participants. Results revealed self-assessed moderate understanding and positive perception of bioeconomy, but poor knowledge of bioeconomy products. The recommendation is that bioeconomy development initiatives should target improvement of individuals’ knowledge of bioeconomy, and awareness of bioeconomy products, and reinforce environmental benefits, and climate action attributable to bioeconomy to drive its adoption among the populace

Equilibrium studies of cadmium biosorption by presumed non-viable bacterial strains isolated from polluted sites

Presumed non-viable high resistant Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia AL96Co, Corynebacterium kutscheri FL108Hg, and Rhodococcus sp AL03Ni were studied for Cd2+ adsorption potentials. Moderate temperature, acidic pH, and high ionic strength were required for bacterial-sorption of cadmium, attaining isothermic equilibrium within 20 min. Experimental cadmium-biosorption data fitted well into biosorption isotherms. The adsorption capacities of the bacterial cell masses spanned 0.003–0.009 l mg−1 (Langmuir model) and 0.43–0.68 (Freundlich model), while binding capacity ranged from 1.14 to 56.16 mg gdw−1, with maximum achievable cadmium uptake of 62.07–109.37 mg gdw−1. The bacteria selectively removed the metal at low concentration (100.0 mg l−1) with an efficiency ranging from 50.0% to 80.0%, while approximately 80.0–92.0% removal efficiency was obtained at higher ionic concentrations (450.0 mg l−1). About 92.66% of the adsorbed metal was recovered from strain CA207Ni upon desorption, and approximately 91.7% of Cd2+ in solution was re-adsorbed onto the biomasses. In this work, effective feasible biosorption of Cd2+ in simulated wastewater system at harsh physico-chemistry, using non-viable resistant bacterial strains was demonstrated. The results indicate that the bacterial strains are sustainable tools for the detoxification of cadmium ions in industrial effluents via wastewater treatment, and cadmium demobilisation in contaminated ecosystem

Biodegradation of petroleum hydrocarbons in the presence of nickel and cobalt

Bioremediation of environments co-contaminated with hydrocarbons and heavy metals often pose a challenge as heavy metals exert toxicity to existing communities of hydrocarbon degraders. Multi-resistant bacterial strains were studied for ability to degrade hydrocarbons in chemically defined media amended with 5.0 mM Ni2þ, and Co2þ. The bacteria, Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia AL96Co, and Corynebacterium kutscheri FL108Hg, utilized crude oil and anthracene without lag phase at specific growth rate spanning 0.3848–0.8259 per day. The bacterial populations grew in hydrocarbon media amended with nickel (Ni) and cobalt (Co) at 0.8393–1.801 days generation time (period of exponential growth, t ¼ 15 days). The bacteria degraded 96.24–98.97, and 92.94–96.24% of crude oil, and anthracene, respectively, within 30 days without any impedance due to metal toxicity (at 5.0 mM). Rather, there was reduction of Ni and Co concentrations in the axenic culture 30 days post-inoculation to 0.08–0.12 and 0.11– 0.15 mM, respectively. The metabolic functions of the bacteria are active in the presence of toxic metals (Ni and Co) while utilizing petroleum hydrocarbons for increase in biomass. These findings are useful to other baseline studies on decommissioning of sites co-contaminated with hydrocarbons and toxic metals

Chromium (VI) biosorption properties of multiple resistant bacteria isolated from industrial sewerage

Chromium (VI) [Cr (VI)] biosorption by four resistant autochthonous bacterial strains was investigated to determine their potential for use in sustainable marine water-pollution control. Maximum exchange between Cr (VI) ions and protons on the cells surfaces were at 30–35 °C, pH 2.0 and 350–450 mg/L. The bacterial strains effectively removed 79.0–90.5 % Cr (VI) ions from solution. Furthermore, 85.3–93.0 % of Cr (VI) ions were regenerated from the biomasses, and 83.4–91.7 % of the metal was adsorbed when the biomasses was reused. Langmuir isotherm performed better than Freundlich isotherm, depicting that Cr (VI) affinity was in the sequence Rhodococcus sp. AL03Ni > Burkholderia cepacia AL96Co > Corynebacterium kutscheri FL108Hg > Pseudomonas aeruginosa CA207Ni. Biosorption isotherms confirmed that Rhodococcus sp. AL03Ni was a better biosorbent with a maximum uptake of 107.46 mg of Cr (VI) per g (dry weight) of biomass. The results highlight the high potential of the organisms for bacteria-based detoxification of Cr (VI) via biosorption

Microbial population changes in tropical agricultural soil experimentally contaminated with crude petroleum

Impacts of crude petroleum pollution on the soil environment and microbial population dynamics as well as recovery rates of an abandoned farmland was monitored for seven months spanning the two major seasons in Nigeria with a view to establishing process conditions necessary for development of effective strategies for bioremediation. The physico-chemistry of the control and contaminated soils differed just significantly (P < 0.05). Whereas these factors were relatively stable over the period of investigation for the control site, a downward trend was observed for the experimental. The polluted soil showed significant diversity in structure and number of flora .There was an initial drop in microbial population densities at the onset of pollution but, a gradual increase was observed thereafter. Higher counts of microflora were obtained for April, May, June and July samples which coincided with the onset and peak of wet season. A rapid and significant reduction in residual oil concentration was observed during this period. Overall, nearly 100% of the crude oil pollutant was degraded within the 28- week study period. The residual oil concentration gave a high but negative correlation coefficient (r = - 0.84 to -0.90) with total heterotrophic and hydrocarbon-utilizing populations. On application of data generated to model equations, approximately 60.5 weeks would elapse before the contaminated soil could recover from the impact of the oil. Our results show that a natural population readily able to degrade crude oil is present in the soil chosen for this study. However, it may be necessary to monitor the level of inorganic nutrients and adjust some appropriately to enhance biodegradation of the organic pollutant

Bacteria with dual resistance to elevated concentrations of heavy metals and antibiotics in Nigerian Contaminated Systems.

Samples of soil, water, and sediments from industrial estates in Lagos were collected and analyzed for heavy metals and physicochemical composition. Bacteria that are resistant to elevated concentrations of metals (Cd2+, Co2+, Ni2+, Cr6+, and Hg2+) were isolated from the samples, and they were further screened for antibiotic sensitivity. The minimum tolerance concentrations (MTCs) of the isolates with dual resistance to the metals were determined. The physicochemistry of all the samples indicated were heavily polluted. Twenty-two of the 270 bacterial strains isolated showed dual resistances to antibiotics and heavy metals. The MTCs of isolates to the metals were 14 mM for Cd2+, 15 mM for Co2+ and Ni2+, 17 mM for Cr6+, and 10 mM for Hg2+. Five strains (Pseudomonas aeruginosa, Actinomyces turicensis, Acinetobacter junni, Nocardia sp., and Micrococcus sp.) resisted all the 18 antibiotics tested. Whereas Rhodococcus sp. and Micrococcus sp. resisted 15 mM Ni2+, P. aeruginosa resisted 10 mM Co2+. To our knowledge, there has not been any report of bacterial strains resisting such high doses of metals coupled with wide range of antibiotics. Therefore, dual expressions of antibiotics and heavy-metal resistance make the isolates, potential seeds for decommissioning of sites polluted with industrial effluents rich in heavy metals, since the bacteria will be able to withstand in situ antibiosis that may prevail in such ecosystems