ABSTRACT
Aims: To determine effects of aromatic hydrocarbons and marine sediments from Niger Delta on the growth of microalga Phaeodactylum tricornutum. Study Design: Fifteen treatments and the control were designed in triplicates in which long cells containing 25 mL of the algae-toxicant dilutions were supplemented with 0.0 mg /L, 1.0 mg /L, 1.8 mg /L, 3.2 mg /L, 5.6 mg /L, and 18.0 mg /L of xylene, anthracene and pyrene each; three sediments and potassium dichromate incubated for 3 days at 20 ± 2°C. The fifteen treatments and control (K2Cr2O7) designated as C0, C1, C2, C3, C4 and C5 were used to determine their median effective concentration (ErC50) on the growth of microalga Phaeodactylum tricornutum. Place and Duration of Study: Department of Microbiology, Chukwuemeka Odumegwu Ojukwu University, Uli Nigeria between February, 2018 and July, 2018. Methodology: A laboratory scale study was carried on the sediment samples from the three studied areas using physiochemical analysis and marine microalga toxicity test. Results: The findings revealed that the three sampling sites contain higher quantities of aromatic hydrocarbons, heavy metals and other physio-chemical parameters in the sediment samples than water samples. The K2Cr2O7had the highest ErC50 value of 08.07 ± 0.03 mg /L with CV and r2 values of 68.61% and 0.99 while pyrene in Nembe sediment had the least ErC50 value of 04.63 ± 0.01 mg /L with CV and r2 values of 78.27% and 0.98 with very strong significant positive linear relationship between algal number and sample concentrations (P = .05). Conclusion: Thus, the toxicity results (> 1 mg /L <EC50 ≤ 10 mg /L) in this study are in line with other toxicity values for this type of toxicants, and are therefore considered to be scientifically relevant in ecotoxicological risk assessment of Niger Delta, Nigeria.
ABSTRACT
Aims: To explore the phylogenetic framework of bacteria isolated from contaminated marine environments of Niger Delta and the expression of the metabolic genes coding for aromatic hydrocarbon degradation and surfactant production. Study Design: Nine treatments designs were set up in triplicates containing 25 mL of sterile modified mineral basal medium supplemented with nine marine hydrocarbon degraders incubated at 24°C for 5 days. Three of the set ups were supplemented each with 1 mg /L of xylene, anthracene and pyrene. Place and Duration of Study: Department of Environmental Sciences, University of South Africa, Pretoria, South Africa between September, 2015 to December, 2017. Methodology: A laboratory scale study was carried on six composite samples of the sediment and water samples from the three studied areas using enrichment, screening, selection, characterization, and PCR assays to explore the phylogenetic framework and metabolic genes expression of the marine bacteria for aromatic hydrocarbon degradation and surfactant production. Results: The findings revealed that there was significant abundance of THB (P = .05) more than TCHUB and more xylene degraders than anthracene and pyrene degraders in the sediment and water samples respectively. The phylogenetic correlational analysis revealed that all the nine selected best degraders out of 48 isolates from the studied area were evolutionary related belonging to the genera: Providencia, Alcaligenes, Brevundimonas, Myroides, Serratia, and Bacillus; able to significantly (P = .05) utilize the all the aromatic hydrocarbons. The existence of catabolic and surfactant genes namely catechol dioxygenase (C23O), rhamnolipid enzyme (rhlB) and surfactin /lichenysin enzyme (SrfA3 /LicA3) genes were detected in only four (4) out of the nine (9) marine aromatic degrading bacteria with 881 base pairs sizes. Conclusion: Thus, the study revealed that these bacterial strains especially Serratia marcescens XYL7 might possess metabolic genes for in situ aromatic hydrocarbon degradation and surfactant production.