[Thomas Beu]

Hi Maurice,
did you ever heard from Archaea, in former times labeled as Archebacteria? These are single-celled microorganisms like bacteria, but standing in their own domain besides the domains of bacteria and eukaryota (all multi-cellular creatures like animals or plants). In spite of many similarities with bacteria, archaea provide a phylogenetical older group with big structural differences to bacteria like completely other cellular membranes for example. Archaeae are often specialized to very harsh conditions like high temperatures (up to 110°C), high concentrations of NaCl, and very high or low pH-values (down to nearly 0). Simultaneously, archaeae are to be found in all types of environments like deep sea, arctic conditions, deserts, all kind of soils, fresh water habitats and so on. Archaea are playing a very important role in the global chemical cycles of Carbon, Nitrogen and Sulfur. So, we can act on the assumption that these microorganisms are a vital part in the cycles of matter in blackwater-habitats and in blackwater-tanks too.
Besides that, some bacteria-species are specialized to grow under lower pH-values as well. One example is that the decomposition of leaf-litter in tropical peat-swamp forests under low pH-values is managed by bacteria (and surely archaea) (Yule and Gomez, 2009).
Thomas