Dear all,
I've found highly diverse and actively expressed genes related to aromatic carboxylic acids degradation from sponge-associated microbes. However I am not aware of the sources of aromatic carboxylic acids in marine ecosystems (I googled "marine aromatic carboxylic acids" but didn't get any luck). I think aromatic carboxylic acids could be the alternate carbon sources for microbes, but I am not quite sure.
Dear Fang,
In a study entitled "Microbial gene functions enriched in the Deepwater Horizon deep-sea oil plume " published in 2012 in The ISME Journal there is a description of indigenous microbes present in this environment that degrade a variety of organic compounds (aliphatic & aromatic) and utilize them as their source of energy. Among those compounds are aromatic carboxylic acids found in the oil spills into the water.
The following are some important paragraphs taken from the article:
The clean-up of the deep-sea oil plume will primarily depend on the indigenous microbes present in this environment, as current technology does not allow removing the dispersed oil and gas at such great depths. One of the critical environmental questions is whether microorganisms for degrading various HCs exist in the community and whether they respond to oil spill. Our GeoChip results indicated that many functional genes/populations involved in both aerobic and anaerobic degradation of various oil components are detected and/or enriched in the oil plume, indicating that the indigenous HC-degrading populations are capable of responding to the oil spill. For example, alkB for alkanes, Xamo for alkene, genes bco, ohbAB, GCoADH and pimF for benzoate, genes mdlA, mdlB and mdlC for mandelate, and genes Apc and catB for BTEX metabolic pathway exhibited a significantly (P
I concur with Dr. Karaman that these, as other microbes, use these and other aromatic compounds as C sources and for energy. It is interesting that you are seeing them in sponge habitats, given that anaerobic bacterial photosynthesis cannot occur in oxic parts of the ocean, and sponges are aerobic. Such carboxylic aromatic compounds are often present in anoxic conditions. However, Imhoff and Truper found that some sponges produce antibiotically active substances. In other words, the microbes may well be producing these compounds symbiotically with the sponges. For example, the sponges serve as habitat for sulfate-reducing bacteria, and the H2S produced makes a microscopic, anoxic environment, so that photosynthetic electron donation occurs. Also, phototrophic bacteria from elsewhere (e.g. muds high in sulfide) could be transported advectively to the sponges, and are ingested.
Dr. Vallero, thanks for your answer. Could you please explain more about the "Such carboxylic aromatic compounds are often present in anoxic conditions"?Do you mean carboxylic aromatic acids are derived from sulfate-reducing metabolism? And by "Imhoff and Truper found that some sponges produce antibiotically active substances", do you mean carboxylic aromatic compounds could function as antibiotics? Thanks.
I assume the authors (Imhoff, Johannes F., and Hans G. Trüper. "Marine sponges as habitats of anaerobic phototrophic bacteria." Microbial ecology 3.1 (1976): 1-9.) are describing the function of the compounds produced by the bacteria in the sponges, i.e. some of the compounds produced and released by the bacteria aid in competition with other organisms. So, yes, the CAA's may well be released for that purpose.
Regarding my comment about anoxic conditions, sponges live exclusively in oxygen-rich conditions, i.e. oxic oceanic zones, but the vast majority of phototrophic bacteria species require anaerobic and sulfide-rich habitats. Thus, from a gross, "macro" perspectives, one would not expect the two organisms, i.e. sponges and phototrophic bacteria to co-exist. So, I am assuming, perhaps incorrectly, that phototrophic bacteria are producing the CAA's, which on its face appears to be counterintuitive. Note that I said this would be unexpected at the macro scale. It is certainly not unusual to have anoxic and oxic conditions "within" the organism. For example, cud-chewing mammals, e.g the cow, produces rumen in anaerobic digestive chambers. The cow is certainly aerobic organism! So, one explanation is that within the sponge, there are regions where the CAA's could be produced the sponge's endogenous bacteria as they compete with other microbes, i.e. antibiotically. However, other possibilities exist, e.g. the compounds were transported from a reduced environment to the oxidized environment where the sponges live. Often, several mechanisms operate simultaneously, so both of these and others may be at work in producing/transporting/transforming your CAA's.
PS - Given your original question, it seems to me that it is easier to make the case for a microbial benefit at the microbial ecology scale. What might be particularly interesting is the extent to which the benefit is conferred upon higher scales and trophic states, the sponge itself and its relationship with other species up the food chain. Perhaps, you could investigate the genomes and genetic signals that influence and that are influenced by these benefits (and disadvantages). Indeed, the carbon and energy benefits are a given but, as we see in co-metabolism, the production of the compounds may also be fortuitous.
Thank you Dr. Vallero for the beautiful and extensive explanation. The anaerobic microenvironments are actually quite prevalent in sponges. Though it hasn't been published, scientists from Isreal have found that in some sponges, the anoxic zones could last for hours (even in their water canals) and sometimes the pumping activities were completely interrupted. I couldn't figure out the possible sources of aromatic compounds in sponges till now. The metabolism of phototrophic bacteria as you suggested, the PBDEs from marine heterotrophic bacteria, the aromatic carboxylic acids derived from plants and animals, as well as human activities could all contribute to the existence of aromatic compounds in sponges. In my study, I also found there was a negative correlation between the aromatics removal and starch utilization, which implied aromatics were utilized by microbes as nutrition. Additionally, the aromatics degrading gene diversity correlated positively with the bacterial microdiversity.
Very interesting! I wonder if the sponge-phototropic bacteria relationships could serve as indicators for some of the processes you mention. Perhaps you could construct an index that would be useful for science-based decisions, e.g. risk assessments, early warning systems, and even threatened/endangered species determinations.
- Badges
- Science method
- Similar topics
- Biological Science
- Ecology