/pdf/processes-of-carbonate-precipitation-in-modern-microbial-176vfhaypi.pdf

Processes of carbonate precipitation in modern microbial mats

Bioremediation of high molecular weight polycyclic aromatic hydrocarbons: a review of the microbial degradation of benzo[a]pyrene.

Biotechnology in petroleum recovery: The microbial EOR

Candida albicans readily forms biofilms on the surface on indwelling medical devices, and these biofilms serve as a source of local and systemic infections. It is estimated that 27% of nosocomial C. albicans bloodstream infections are polymicrobial, with Staphylococcus aureus as the third most common organism isolated in conjunction with C. albicans. We tested whether S. aureus and C. albicans are able to form a polymicrobial biofilm. Although S. aureus formed poor monoculture biofilms in serum, it formed a substantial polymicrobial biofilm in the presence of C. albicans. In terms of architecture, S. aureus formed microcolonies on the surface of the biofilm, with C. albicans serving as the underlying scaffolding. In addition, S. aureus matrix staining revealed a different phenotype in polymicrobial versus monomicrobial biofilms, suggesting that S. aureus may become coated in the matrix secreted by C. albicans. S. aureus resistance to vancomycin was enhanced within the polymicrobial biofilm, required viable C. albicans, and was in part mediated by C. albicans matrix. However, the growth or sensitivity to amphotericin B of C. albicans is not altered in the polymicrobial biofilm.

https://aac.asm.org/content/aac/53/9/3914.full.pdf

Candida albicans and Staphylococcus aureus Form Polymicrobial Biofilms: Effects on Antimicrobial Resistance

Homoacetogenesis during hydrogen production by mixed cultures dark fermentation: Unresolved challenge

Microbial enhanced oil recovery (MEOR)

When biofilms (aggregations of bacteria and extracellular polymer secretions) in samples from the Carter Sandstone of Alabama were prepared for scanning electron microscopy (SEM) using different dehydration techniques, the organic material had visibly different textures and distributions. In order to assess whether the variation was attributable to sample preparation or to inherent biofilm heterogeneity, each of five techniques were tested 3 to 10 times on small (1 cm) pieces of the Carter Sandstone containing either a strain of bacteria cultured from and reintroduced into the rock, or an in situ biofilm grown by injection of nutrients through core samples. The techniques tested were (1) air drying alone; (2) fixation in 10% glutaraldehyde with air drying; (3) ethanol dehydration with hexamethyldisilazane (HMDS) drying [2.5% glutaraldehyde, ethanol dehydration, and HMDS]; (4) ethanol dehydration with critical-point drying; and (5) ethanol and acetone dehydration with critical-point drying. Unpreserved control samples were either imaged wet in an environmental scanning electron microscope (ESEM) or vacuum-dried for SEM. Observations were based on SEM microscopy of over 60 samples and study of over 150 photomicrographs. In both experiments, the original morphology of individual bacteria was best preserved by ethanol dehydration with HMDS drying, ethanol dehydration with critical-point drying, or ethanol-acetone dehydration with critical-point drying. Critical-point drying preserved bacteria but stripped away mucilaginous material, revealing filamentous structures within the biofilm. These filaments, along with masses of microspheres (nannobacteria?) and the smooth mucilaginous outer layer, also occur in wet samples studied by ESEM, and are, therefore, not dehydration artifacts. However, different sample preparation techniques accentuated different components of the heterogeneous biofilm, thus resulting in vastly different textures. The cultured bacteria produced a biofilm that had a different surface texture and was more susceptible to sample preparation artifacts than the in situ biofilm. Use of more than one sample preparation technique is recommended in order to avoid bias.

Effects of SEM Preparation Techniques on the Appearance of Bacteria and Biofilms in the Carter Sandstone

Methanogenesis under acidic pH conditions in a semi-continuous reactor system.

A method was developed to deposit a visible layer of water-insoluble compounds via sublimation onto the surface of solid media. The compound is sublimed from a heated aluminum dish containing the compound onto the surface of an inverted, ice-cooled, inoculated agar petri dish. The method results in the deposition of a thin, even layer on the agar surface without the use of solvent. After incubation, clearing zones around colonies indicate the presence of compound-degrading microorganisms.

Lewis R. Brown

Papers

Microbial enhanced oil recovery (MEOR)

Effects of SEM Preparation Techniques on the Appearance of Bacteria and Biofilms in the Carter Sandstone

Methanogenesis under acidic pH conditions in a semi-continuous reactor system.

Use of sublimation to prepare solid microbial media with water-insoluble substrates.

Slowing Production Decline and Extending the Economic Life of an Oil Field: New MEOR Technology