Biodegradation is a viable bioremediation technology for various pollutants. It has long been known that microorganisms degrade environmental pollutants, such as carbzole, crude oil, fluorine and pyrene, in various matrices and environments. Biodegradation is a broad field and involves the use of a wide range of microorganisms to break chemical bonds.
The genus Gordonia has attracted much interest in recent years due to their ability to degrading xenobiotics, environmental pollutants or slowly biodegradable natural polymers as well as to transform or synthesize possibly useful compounds. However, there has been little research so far on the ability of microorganisms in the genus Gordonia to degrade and assimilate n-alkanes.
Taxonomic studies were performed on a novel carotenoid-producing strain, designated A2T, isolated from crude oil-contaminated soil. The phylogenetic tree of 16S rRNA gene sequence analysis showed that the strain A2T was closely related to Gordonia amicalis KCTC 9940T. DNA-DNA relatedness of strain A2T with respect to its closest phylogenetic neighbors was 65.7% for G. amicalis NBRC 9940T. Based on the phylogenetic, chemotaxonomic, and phenotypic data, strain A2T is concluded to represent a novel species of the genus Gordonia, for which the name Gordonia ajoucoccus sp. nov. is proposed. The type strain is A2T (=KCTC 11900BPT = CECT 8382T). The caronteoid of γ-carotene and keto-γ-carotene is synthezed from G. ajoucoccus A2T. G. ajoucoccus A2T is also capable of assimilating n-alkanes with a broad range of chain lengths (C6, C8–C25). Batch culture containing 1% (v/v) hexadecane or 1% (v/v) commercial diesel yielded 25 mg/L and 2.6 mg/L of carotenoids from G. ajoucoccus A2T in a bioreactor, respectively. Analysis of hexadecane and hexane degradation metabolites using gas chromatography/mass spectrometry (GC/MS) proposed that G. ajoucoccus A2T may possess a primary alcohol terminal oxidation pathway that allows it to utilize n-alkanes and hexane as carbon sources. Metabolites of the metabolic response of G. ajoucoccus A2T grown on various carbon sources were analyzed using GC/MS. Metabolites such as amino acids, sugars, and organic acids could be identified. Thirty-four metabolites were detected in five replicate samples, and score plots of PLS-DA were generated to comparatively evaluate the effects of consumption of various carbon sources on strain A2T. We reported the draft sequence of strain A2T. It has a 5,029,502-base-pair circular chromosome encoding 4,666 genes, and the genome consists of genes that are involved in denitrification, the alkane degradation pathway, the β-oxidation pathway, the butanol biosynthesis pathway, benzoate degradation, molecule transportation, wax ester synthesis, and other processes.
In our experiments, phylogenetic and phenotypic analyses purposed that this strain A2T represents a novel species with various pathways. In this study, we have identified novel pathways for the degradation of n-alkane and production of secondary metabolites in G. ajoucoccus A2T.
