putida BS3701 attacked the oil globules from the outside (Fig. 4a), whereas Rhodococcus sp. S67 penetrated inside the oil globules (Fig. 4b). Irrespective of their locations, MDV3100 purchase these bacteria, both in pure and mixed culture, secreted large amounts of polysaccharide materials in the form of films and granules (Fig. 4c), which were assessed by electron microscopic examinations of ultrathin sections stained with ruthenium red (Fig. 4d). Cytochemical staining with diaminobenzidine showed that oxidative

enzymes were located in the cell walls of both bacteria as well as in the extracellular films that were evenly distributed over the cell surfaces (Fig. 4e and f). The exocellular substances were most abundant when bacteria were cultivated in a mixed culture. Moreover, the mixed bacterial culture showed a greater efficiency in oil degradation in water medium than the individual bacteria (more than 70% in mixed cultures as compared with 50–60% observed for P. putida BS3701 and Rhodococcus sp. S67 as pure cultures). A 3D reconstruction of bacterial consortia grown on oil

(Fig. 5a and b) was performed to answer the questions: (1) Is there any expediency in the abundant release of polymer substances by microorganisms grown on oil hydrocarbons? (2) Do cells form any specific structures that facilitate the use of potential growth substrates contained in oil? To understand the structural behavior of microorganisms, a bacterial consortium containing

cells of Rhodococcus sp. S67 and P. putida was used as a model. The consortium ABT-199 cost was grown in shaking flasks with crude oil as a sole carbon source. A visual analysis of the 3D features of bacterial structures formed in the oil demonstrated that the bacteria inhabited discrete cavities in the oil droplets that constituted a kind of ‘trophic’ vesicle or granule. All of the granules were bound to one another by polymer films and all of the unified structures comprised a well-developed network over the surface of the oil globules. Granules in the globules were either closed or open to the aqueous medium. Open granules probably served PJ34 HCl as emulsion traps for metabolites generated by oil degradation. The analysis of serial sections showed that after complete utilization of the substrate, the trophic units, or ‘trophosomes,’ broke down and the entire process of the substrate utilization involved a continuous assembly and decay of functional units in the network of exocellular granule vesicles. The present study reveals a possibly common scenario by which different yeasts and bacteria may colonize and utilize hydrophobic substrates as oil and its components (specifically n-alkanes) when suspended as droplets in an aqueous medium. The most notable feature for several of the yeasts studied here was the substrate-induced formation of ‘canals’ that permeated the cell walls and that were lined with exopolymers and oxidative enzymes.