Impact of membrane fatty acid composition on the uncoupling sensitivity of the energy conservation of Comamonas testosteroni ATCC 17454

Biodiversity of the oleaginous microorganisms in Tibetan Plateau

Microbial lipids, which are also known as single cell oils (SCO), are produced by oleaginous microorganisms including oleaginous bacteria, yeast, fungus and algae through converting carbohydrates into lipids under certain conditions. Due to its unique environment having extremely low temperature and anoxia, the Tibetan Plateau is amongst the regions with numerous rare ecotypes such as arid desert, salt marsh, alpine permafrost, hot spring, and lawn. By using a rapid, convenient screening method, we identified 31 strains of oleaginous microorganisms from different habitats in the Tibetan Plateau, which include wetlands, lawn, hot spring, alpine permafrost, and saline-alkali soil. Molecular identity analysis showed that they belong to 15 different species, 7 of which are reported for the first time as lipid-producing microorganisms, that is, Cladosporium sp., Gibberella fujikuro, Ochrobactrum sp., Plectosphaerella sp., Tilletiopsis albescens, Backusella ctenidia, and Davidiella tassiana. The distribution of the oleaginous microorganisms varies with habitats. 11 strains were found in hot spring (35.5%), 10 in farmland (32.3%), 6 in lawn (19.4%), 2 in sand (6.4%), 1 in wetland (3.2%), and 1 in permafrost (3.2%). Carbon utilization analysis indicated that most of these filamentous fungi can use xylose and carboxymethyl cellulose (CMC) as carbon source, where Backusella ctenidia, Fusarium sp. and Gibberella fujikuroi have the strongest capability.

Activity and viability of polycyclic aromatic hydrocarbon-degrading Sphingomonas sp. LB126 in a DC-electrical field typical for electrobioremediation measures

There has been growing interest in employing electro‐bioremediation, a hybrid technology of bioremediation and electrokinetics for the treatment of contaminated soil. Knowledge however on the effect of weak electrokinetic conditions on the activity and viability of pollutant‐degrading microorganisms is scarce. Here we present data about the influence of direct current (DC) on the membrane integrity, adenosine triphosphate (ATP) pools, physico‐chemical cell surface properties, degradation kinetics and culturability of fluorene‐degrading Sphingomonas sp. LB126. Flow cytometry was applied to quantify the uptake of propidium iodide (PI) and the membrane potential‐related fluorescence intensities (MPRFI) of individual cells within a population. Adenosine tri‐phosphate contents and fluorene biodegradation rates of bulk cultures were determined and expressed on a per cell basis. The cells' surface hydrophobicity and electric charge were assessed by contact angle and zeta potential measurements respectively. Relative to the control, DC‐exposed cells exhibited up to 60% elevated intracellular ATP levels and yet remained unaffected on all other levels of cellular integrity and functionality tested. Our data suggest that direct current (X = 1 V cm⁻¹; J = 10.2 mA cm⁻²) as typically used for electrobioremediation measures has no negative effect on the activity of the polycyclic aromatic hydrocarbon (PAH)‐degrading soil microorganism, thereby filling a serious gap of the current knowledge of the electrobioremediation methodology.

Effects of Norway spruce (Picea abies) resin on cell wall and cell membrane of Staphylococcus aureus

Resin salve prepared from Norway spruce (Picea abies) has been used for centuries in traditional medicine to treat skin diseases. The authors studied with transmission and scanning electron microscopy, and with electron physiology, changes in cell wall and cell membrane of Staphylococcus aureus after exposure of the bacterial cultures to resin. After exposure, cell wall thickening, cell aggregation, changed branching of fatty acids, and dissipation of membrane potential of the bacterial cells were observed. The authors conclude that spruce resin affects the cell viability via changes in the cell wall and membrane, and impairs, thereby, the synthesis of energy in the bacteria.