Cellular and extracellular carbohydrates and lipids from marine bacteria during growth on soluble substrates and hydrocarbons

Abstract

The variability of extracellular excretions of 4 marine bacterial strains was investigated during growth on soluble (acetate or lactate) and insoluble (hydrocarbons) substrates. Cellular and extracellular protein, carbohydrate and lipid contents were estimated at the end of exponential growth phase. Emulsifying capacity of the cell-free culture medium was estimated. Lipid classes were characterized by using thin layer chromatography coupled with flame ionization detection. All strains were found to excrete organic compounds in their culture medium whatever the substrate. Carbohydrate and lipid compounds were the main products whereas proteins were excreted in lesser amounts. Nevertheless, the adaptation of the marine strains to insoluble substrate was characterized by enhanced lipid excretions (mainly phospholipids) which correlated well with higher emulsifying activity on this substrate. These excretions represented 8.6 to 156.2 and 4.3 to 101.6 yg per mg bacterial carbon, for carbohydrates and lipids respectively, according to a recent estimate of the bacterial protein to carbon ratio. These data show that inputs of dissolved organic compounds through bacterial activity could have important consequences on the physico-chemical characteristics of seawater in area where bacterial biomass is concentrated.

Bacterial Growth Efficiency in Natural Aquatic Systems

“…It has been suggested that excretion of metabolites is a pathway of energy dissipation that may contribute to the maintenance of intracellular stoichiometry (31a, 84). However, excretion of organic metabolites, including polysaccharides, lipids, proteins, and humiclike substances, has also been found under conditions of carbon and nutrient limitation in aquatic bacteria (48,63,67,146). Most excretion products are polymeric, and the biosynthesis of these substances typically exerts high energy requirements to the cell (117,133).…”

Analysis of Lipid Export in Hydrocarbonoclastic Bacteria of the GenusAlcanivorax: Identification of Lipid Export-Negative Mutants ofAlcanivorax borkumensisSK2 andAlcanivorax jadensisT9

“…(60), Alcaligenes sp. PHY9, and Pseudomonas nautica strain 617 (24), and for the fungus Cladosporium resinae (61), the function of lipid export is unclear. As a part of surface-active compounds (also known as biosurfactants or bioemulsifiers), specialized lipids with a chemical structure different than those investigated in this study could play a role in the modification of medium properties and could therefore enhance the contact between bacteria and water-insoluble hydrocarbons.…”

“…The localization of neutral lipids in marine organisms is not restricted to the cell cytoplasm, as extracellular lipid deposition has been shown in studies with Alcaligenes sp. PHY9 and Pseudomonas nautica (24). The production of extracellular wax esters by Alcanivorax jadensis T9 growing on hexadecane was described a few years ago (11).…”

Environmental Remediation Full-Scale Implementation: Back to Simple Microbial Massive Culture Approaches

“…Since bacterial growth required a direct contact of cells with a solube and/or non-soluble substrate, stimulation by using chemical or biological dispersant (emulsifier, surfactant) will increase degradation rate for many petroleum hydrocarbons compounds such as paraffin [8]; Polycyclic Aromatic Hydrocarbons [9]; crude oil [10,11]. Reference [12] showed high capacity of microbial adhesion to an hydrophobic substrates. We suggest some specific enzymes have been induced and released into liquid media system.…”