A novel anaerobic needle inoculator for strict obligate anaerobic bacteria

Summary An inoculating needle for picking and transferring colonies of strict anaerobic bacteria was built. A self-refilling syringe was adapted to carry a stainless steel needle within the cannula, and a tee junction allowed continuous flushing with dioxygen-free gas.     

Early anaerobic metabolisms

Before the advent of oxygenic photosynthesis, the biosphere was driven by anaerobic metabolisms. We catalogue and quantify the source strengths of the most probable electron donors and electron acceptors that would have been available to fuel early-Earth ecosystems. The most active ecosystems were probably driven by the cycling of H2 and Fe2+ through primary production conducted by anoxygenic phototrophs. Interesting and dynamic ecosystems would have also been driven by the microbial cycling of sulphur and nitrogen species, but their activity levels were probably not so great. Despite the diversity of potential early ecosystems, rates of primary production in the early-Earth anaerobic biosphere were probably well below those rates observed in the marine environment. We shift our attention to the Earth environment at 3.8Gyr ago, where the earliest marine sediments are preserved. We calculate, consistent with the carbon isotope record and other considerations of the carbon cycle, that marine rates of primary production at this time were probably an order of magnitude (or more) less than today. We conclude that the flux of reduced species to the Earth surface at this time may have been sufficient to drive anaerobic ecosystems of sufficient activity to be consistent with the carbon isotope record. Conversely, an ecosystem based on oxygenic photosynthesis was also possible with complete removal of the oxygen by reaction with reduced species from the mantle.     

A procedure for anaerobic column chromatography employing an anaerobic freter-type chamber

A technique is described for the anaerobic fractionation of oxygen-sensitive material. A Freter-type chamber in which the oxygen concentration is maintained at 2 to 5 μl/liter is used in conjunction with anaerobic chromatographic columns that are exterior to the chamber. The column inlet and outlet are connected via thick-walled polyethylene tubing to access ports in the chamber wall. Anaerobic buffer inside the chamber is pumped from the chamber to equilibrate the column. The oxygen-labile sample then is pumped onto the anaerobic column followed by the elution gradient buffer. Column eluate is returned to a fraction collector inside the chamber. At no stage is the sample exposed to air. This technique has been used effectively for fractionation of highly oxygen-sensitive enzymes from methanogenic bacteria where use of other methods failed.     

Air-side ammonia stripping coupled to anaerobic digestion indirectly impacts anaerobic microbiome

Air-side stripping without a prior solid–liquid phase separation step is a feasible and promising process to control ammonia concentration in thermophilic digesters. During the process, part of the anaerobic biomass is exposed to high temperature, high pH and aerobic conditions. However, there are no studies assessing the effects of those harsh conditions on the microbial communities of thermophilic digesters. To fill this knowledge gap, the microbiomes of two thermophilic digesters (55°C), fed with a mixture of pig manure and nitrogen-rich co-substrates, were investigated under different organic loading rates (OLR: 1.1–5.2 g COD l⁻¹ day⁻¹), ammonia concentrations (0.2–1.5 g free ammonia nitrogen l⁻¹) and stripping frequencies (3–5 times per week). The bacterial communities were dominated by Firmicutes and Bacteroidetes phyla, while the predominant methanogens were Methanosarcina sp archaea. Increasing co-substrate fraction, OLR and free ammonia nitrogen (FAN) favoured the presence of genera Ruminiclostridium, Clostridium and Tepidimicrobium and of hydrogenotrophic methanogens, mainly Methanoculleus archaea. The data indicated that the use of air-side stripping did not adversely affect thermophilic microbial communities, but indirectly modulated them by controlling FAN concentrations in the digester. These results demonstrate the viability at microbial community level of air side-stream stripping process as an adequate technology for the ammonia control during anaerobic co-digestion of nitrogen-rich substrates.     

Initial anaerobic biofilm development

Summary The initial rate of methanogen accumulation and anaerobic biofilm accumulation increased with increasing bulk liquid organic space loading and volatile suspended solids concentration. The rates were faster at a 15 day bulk liquid SRT than 5 day SRT. The results indicate that a reduction in start-up time for anaerobic fixed film reactors might be achieved by maintaining high organic space loadings and high concentrations of active microorganisms in the bulk liquid phase during the start-up period.     

Corrinoids in anaerobic bacteria

Abstract C₁-metabolizing bacteria were analyzed for their corrinoids. The autotrophic phototrophe Chloroflexus aurantiacus contains predominantly the light-sensitive coenzyme B₁₂. The corrinoid could be teh prostethic group of a methylmalonyl-CoA mutase, which is involved in the CO₂ fixing reaction sequence from proplonyl-CoA to succinyl CoA. Methanobacterium thermoautotrophicum and Sporomusa ovata contain only traces of light-sensitive corrinoids, indicating that the demethylation reaction is favored, if these corrinoids are involved in methyl transfer reactions. The chemical structure of the unique p -cresolyl cobamide is specific for the acetogenic bacterium S. ovata , rather than the corrinoid 'factor III' for methanogenic bacteria.