Taxonomic and Predictive Functional Profile of Hydrocarbonoclastic Bacterial Consortia Developed at Three Different Temperatures.

Microbial community exhibit shift in composition in response to temperature variation. We report crude oil-degrading activity and high-throughput 16S rRNA gene sequencing (metagenome) profiles of four bacterial consortia enriched at three different temperatures in crude oil-amended Bushnell-Hass Medium from an oily sludge sediment. The consortia were referred to as O (4 ± 2 â„ƒ in 3% w/v crude oil), A (25 ± 2 â„ƒ in 1% w/v crude oil), H (25 ± 2 â„ƒ in 3% w/v crude oil), and X (45 ± 2 â„ƒ in 3% w/v crude oil). The hydrocarbon-degrading activity was highest for consortium A and H and lowest for consortium O. The metagenome profile revealed the predominance of Proteobacteria (62.12-1.25%) in each consortium, followed by Bacteroidota (18.94-37.77%) in the consortium O, A, and H. Contrarily, consortium X comprised 7.38% Actinomycetota, which was essentially low (< 0.09%) in other consortia, and only 0.41% Bacteroidota. The PICRUSt-based functional analysis predicted major functions associated with the metabolism and 5060 common KEGG Orthology (KOs). A total of 296 KOs were predicted exclusively in consortium X. Additionally, 247 KOs were predicted from xenobiotic biodegradation pathways. This study found that temperature had a stronger influence on the composition and function of the bacterial community than crude oil concentration.

Efficiency and kinetics of Assam crude oil degradation by Pseudomonas aeruginosa and Bacillus sp.

We report kinetics of Assam crude oil degradation by Pseudomonas aeruginosa AKS1 and Bacillus sp. AKS2, both isolated from Assam refinery sediments. The isolates exhibited appreciable degrees of hydrophobicity, emulsification index and biosurfactant production. Crude oil degradation efficiency of isolates was assessed in (1) liquid medium amended with 1% v/v crude oil and (2) microcosm sediments (125 mg crude oil/ 10 g sand). In liquid culture, biodegradation rate (k) and half-life (t1/2) values were found to be 0.038 day-1 and 18.09 days for P. aeruginosa AKS1, and 0.020 day-1 and 33.97 days in case of Bacillus sp. AKS2, respectively. In microcosm sediments, the estimated k and t 1/2 values were 0.014 day-1 and 50 days for P. aeruginosa AKS1, and 0.011 day-1 and 61.34 days in case of Bacillus sp. AKS2. The level of nutrient treatment in microcosm sand sediment was 125 µg N and 62.5 µg P/g sediment in case of P. aeruginosa AKS1 and 375 µg N and 37.5 µg P/g sediment in case of Bacillus sp. AKS2. In microcosms without inorganic nutrients, values of k and t1/2 were found to be 0.007 day-1 and 100 days for P. aeruginosa AKS1 and for Bacillus sp. AKS2, the respective values were 0.005 day-1 and 150.68 days. Our data provides important information for predictive hydrocarbon degradation in liquid medium and contaminated sediments.

Hydrocarbon degradation potential and competitive persistence of hydrocarbonoclastic bacterium Acinetobacter pittii strain ABC.

Acinetobacter pittii strain ABC was isolated from oily sludge sediments and characterized with regard to utilization/degradation of hydrocarbons and competitive persistence in hydrocarbon-amended media. The isolate grew in both aliphatic- and aromatic hydrocarbon-amended Bushnell-Haas medium (BHM). When incubated in 1% (v/v) Assam crude oil-amended BHM for 5 and 10 days, this strain was able to degrade 88% and 99.8% of the n-hexane extractable crude oil components, respectively. The isolate showed appreciable emulsification index (E24 65.26 ± 1.2%), hydrophobicity (60.88 ± 3.5%) and produced lipopeptide biosurfactant (0.57 g L-1). The isolate was able to tolerate heavy metal salts at concentrations reported in crude oil-polluted sediments from Assam. A 16S rDNA DGGE-based screening showed the persistence of A. pittii strain ABC in hydrocarbon-amended microcosms co-inoculated with other hydrocarbonoclastic bacterial strains (Pseudomonas aeruginosa AKS1, Bacillus sp. AKS2, Arthrobacter sp. BC1, and Novosphingobium panipatense P5:ABC), each isolated from the same oily sludge sediment. These findings indicate A. pittii strain ABC as a potential agent for the bioremediation of crude oil-polluted environment.