Program

Petroleum is a widespread organic pollutant in marine environments. Biodegradation is the most important process involved in the natural attenuation and eventual removal of petroleum from the environment. Petroleum is a complex mixture, since different bacteria play different roles in oil biodegradation, a mixed culture with different bacteria carrying complementary oil-degrading abilities are needed to clean up oil pollutants. Thus, apart from isolating oil-degrading bacteria, revealing the interactions among oil-degrading species and degrading-assistant species, and identifying the functionally active populations is a critical issue for oil bioremediation. However, few studies have addressed this issue. Here, we setup two enrichment groups with mangrove sediments and diesel oil. One was transfer enrichment which transferred the enriched culture into new medium weekly as in the traditional procedure, another was non-transfer enrichment which incubated the slurry without any subculture. Our goal is to apply large amounts of 16S rRNA marker gene sequences into well-established analytical tools including: Quantitative Insights Into Microbial Ecology (QIIME) to provide a comprehensive picture of the phenotypic and genotypic succession of the microbial community; the phylogenetic molecular ecological networks (pMENs) to reveal microbial key population and interaction during incubation time; phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) to predict the functional metabolic of microbial communities after contamination. Microbial composition profile indicated microbial community of non-transfer enrichment was constructed by several orders such as Sphingomonadales (Novosphingobium), Pseudomonadales (Pseudomonas), Oceanospirillales (Alcanivorax), Flavobacteriales (Muricauda) that distributed similarly during the incubation period. Sphingomondales is the dominant order in the transfer enrichment. Furthermore, the pMENs exhibited the key oil-degrading bacterial population in non-transfer enrichment such as Alcanviorax, Muricauda, and Parvibaculum coexist to order Sphingomonadales. Sphingomondales as the key population in transfer enrichment exhibited competitive relationship with endogenous bacteria orders such as Pseudomonadales and Rhodobacterales. PICRUSt results exhibit non-transfer enrichment had broad metabolism with greater extensive niche than transfer enrichment. Further PICRUSt identified that aromatic hydrocarbon degradation gene nahAc which was abundant in Transfer enrichment were contributed by Sphingomonadales, and alkanes degradation  alkB which was abundant in non-transfer enrichment were distributed by Pseudomonadales Oceanospirillales, and Flavobacteriales. We hypothesized the interaction of Sphingomonadales toward other oil-degrading bacteria changed by the constant addition of petroleum diesel fuel. The present study is among the first to document that the network interactions among different phylogenetic populations in mangrove microbial communities were substantially altered by addition of petroleum hydrocarbon.

Keywords: Mangrove sediment; Microbial community; Molecular ecological networks; Oil biodegradation