Proteomic analysis of Marinobacter hydrocarbonoclasticus SP17 biofilm formation at the alkane-water interface reveals novel proteins and cellular processes involved in hexadecane assimilation

Abstract

Many hydrocarbon degrading bacteria form biofilms at the hydrocarbon-water interface to overcome the low accessibility of these poorly water-soluble substrates. In order to gain insight into the cellular functions involved, we undertook a proteomic analysis of Marinobacter hydrocarbonoclasticus SP17 biofilm developing at the hexadecane-water interface. Biofilm formation on hexadecane led to a global change of the cell physiology involving modulation of the expression of 573 out of 1144 detected proteins when compared with planktonic cells growing on acetate. Biofilm cells overproduced a protein, encoded by MARHY0478 that contains a conserved domain belonging to the family of the outer membrane transporters of hydrophobic compounds. Homologs of MARHY0478 were exclusively found in marine bacteria degrading alkanes or possessing alkane degradation genes and hence presumably constitute a family of alkane transporter specific to marine bacteria. Interestingly, we also found that sessile cells growing on hexadecane overexpressed type VI secretion system components. This secretion system has been identified as a key factor in virulence and in symbiotic interaction with host organisms. This observation is the first experimental evidence of the contribution of a type VI secretion system to environmental adaptation and raises the intriguing question about the role of this secretion machine in alkane assimilation.

Perspective: what is known, and not known, about the connections between alkane oxidation and metal uptake in alkanotrophs in the marine environment

“…15 These transporters include OprG, an ABC transporter that is thought to be a low affinity transporter of iron. A recent proteomics paper from Grimaud et al 16 reported no increase in AlkB when Marinobacter hydrocarbonoclasticus SP17 cells are grown on alkanes. This has been attributed to the known difficulty in extracting and detecting integral membrane proteins with 2D electrophoresis.…”

Nooks and Crannies in Type VI Secretion Regulation

“…Similarly, the T6SS gene cluster of the plant pathogen Pseudomonas fluorescens is induced by the presence of necrotic roots (7). The expression of several T6SS, including those of Vibrio parahaemolyticus, P. aeruginosa HSI-1 and HSI-3, and Marinobacter hydrocarbonoclasticus, is upregulated in static cultures or in biofilm compared to expression under planktonic conditions (1,2,38,99,105,108). Interestingly, the P. aeruginosa HSI-1 and HSI-3 loci are induced at different times during biofilm development: the expression of HSI-1 increases progressively during biofilm formation (from attachment to maturation), whereas HSI-3 is temporarily induced during the initial steps of biofilm development (99).…”

Genome Sequence of the Marine Bacterium Marinobacter hydrocarbonoclasticus SP17, Which Forms Biofilms on Hydrophobic Organic Compounds

“…Physiological and proteomic studies revealed that biofilm formation is an efficient strategy to colonize hydrophobic interfaces (1,11,12). SP17 forms biofilms at the interface between aqueous-phase and HOC substrates like n-alkanes, fatty alcohols, or apolar lipids, such as wax esters and triacylglycerols.…”