Organic matter biodegradation proceeds via multiple enzymatic reactions, involving different oxidants as well as a number of intermediate compounds. Microbial reworking of organic matter can result in a substantial microbial contribution to the total organic matter pool. The investigations of the mechanisms, which can alter the microbial metabolism in marine sediments, are essential for understanding diagenetic processes, especially at those environments with toxic metal concentrations. Metals can bind with cells components, affecting their functioning. Consequently, the organic matter oxidation in the cellular metabolism may be affected. By contrast, the carbon sources are discriminated between labile and refractory organic compounds. The labile portion of organic matter mainly consists of biopolymers and includes carbohydrates, lipids, and proteins. The aim of this chapter is to present the main results of 10 years of studies regarding the organic matter oxidation by bacterial consortia under toxic metal levels on a tropical estuarine environment surrounded in part by mangrove areas. As the main find, the chronic dominance of lipids and carbohydrates at estuaries and mangroves systems may change the bacterial trophic state from aerobic to anaerobic metabolism. This alteration may reflect on decreasing both bacterial efficiency of organic matter degradation and bacterial productivity. Further, when these systems show high levels of metals at the sediment, the metabolic efficiency is even lower because, although bacteria consortia is able to produce extracellular polymeric substances (EPS) as defense mechanism, multimetal contamination may hinder bacterial organic matter oxidation through dehydrogenase activity inhibition.
Part of the book: Biodegradation and Bioremediation of Polluted Systems