engleski

Sponge activity in situ - Biotechnological and ecological implications

Sponges as so called inner filter feeders are actively producing a current through their bodies thus aspiring food and oxygenated water. Descriptions of anaerobic microbes inhabiting sponge mesohyls have questioned the general assumption of a permanently well-oxygenated sponge tissue. Assumptions of anaerobic processes and anoxic conditions in sponges, however, not only result in implications on biotechnological issues like in vitro culture approaches and nutrient supply. They also suppose a possible regulatory mechanism for sponges to control associated microorganisms by providing an ecologically challenging habitat by changing from aerobic to anaerobic states only allowing adapted organisms to persist within sponges. As various activitiy patterns are already published the pumping activity would allow sponges to actively control not only their inhabitants but also their inhabitants metabolisms by switching from an aerobic to an anaerobic state. Microelectrode measurements on Aplysina aerophoba in the lab showed that this species is well oxygenated when pumping, but when it stops pumping, the major part of the tissue turns anoxic within minutes. We therefore investigated the pumping behaviour of Aplysina aerophoba in situ and present the resulting implications on possible metabolic interactions as well as the biotechnological implications. To address this question in a non-invasive manner we employed SCUBA diving techniques and snorkelling. A tracer was applied in situ to visualize the water current through 2.144 oscules on 259 individual Aplysina at different seasons and different daytimes. Negative effects of the tracer used on the sponges` activity could be excluded by control experiments. All oscules investigated were active and showed a clear tracer discharge. Therefore we deduce a permanent aerobic condition for Aplysina aerophoba tissue in situ. This fits with the detection of betaproteobacterial 16S rRNA genes of the Nitrosospira group and of genes encoding for ammonia monooxygenase (amoA). In contrast, no 16S rRNA genes of anaerobic ammonium oxidizers (anammox) or genes encoding for nitrite reductase (nirK) of denitrifying bacteria could be found in Aplysina aerophoba and associated bacteria.

Sponge activity in situ

nije evidentirano