Maryam Bello-Akinosho, Rasheed Adeleke, Dirk Swanevelder and Mapitsi Thantsha
Agricultural Research Council, Institute for Soil Climate and Water, Pretoria, South Africa
Bacteria isolates with diverse capabilities relevant in different biological processes in the ecosystem such as bioremediation and soil fertility are in high demand in the mining and agroforestry sectors. The ultimate aim of any bioremediation process is to restore polluted land. It therefore becomes imperative that bacteria that can both metabolise pollutants and perhaps, also possess capabilities that can be additionally exploited to improve soil fertility, are utilised. Fourty-five polycyclic aromatic hydrocarbon - degrading bacteria were isolated from enriched cultures of engine-oil polluted soil. The isolates were identified by partial 16S rRNA sequence analyses as members of the genera Pseudomonas, Acinetobacter, Arthrobacter, Rhodococcus, Bacillus, Microbacterium, Ochrobactrum and Stenotrophomonas. The predominant ones belong to the phyla Firmicutes, Actinobateria and Proteobacteria. The isolates were investigated for their ability to solubilise indissoluble phosphate, fix atmospheric nitrogen and produce indoleacetic acid (IAA) as a way to ascertain their potential capabilities of contributing to soil fertility and eventually to restorative remediation. One of the isolates, Pseudomonas sp. strain 10-1B was sequenced on Illumina MiSeq sequencer using the Nextera sample preparation kit and the 300bp paired-end V3 Illumina chemistry. The genome was annotated using the NCBI Prokaryotic Genomes Automatic Annotation Pipeline. The draft genome was predicted to compose of 5,584 protein-encoding genes and 5,361 coding sequences (CDSs) in addition to 71 RNAs, of which 65 are tRNAs. In addition, several dioxygenases, reductases, ferredoxin, dehydrogenases and Rieske proteins known to play active role in biodegradation processes were identified. Other genes, such as phosphatases known to play an active role in phosphates solubilisation and 1-aminocyclopropane-1-carboxylate deaminase, known to promote root elongation, were also identified on the genome. Each of the isolates, except Stenotrophomonas, showed at least one of the tested traits related to soil fertility with many of them displaying two or all three of these properties. Generalised linear modelling statistical approaches were applied to evaluate the contribution of the four most represented genera (Pseudomonas, Acinetobacter, Arthrobacter and Rhodococcus) to soil fertility. The Pseudomonas isolates were the most promising in all three soil fertility improvement traits evaluated. These findings demonstrate a clear potential of the isolates to participate in restorative bioremediation of polluted soils which is of immense benefit in the agroforestry and mining sectors.