In situ characterization of substrate uptake by Microthrix parvicella using microautoradiography

Abstract

Microthrix parvicella is a filamentous microorganism responsible for bulking and foaming problems in many activated sludge treatment plants. The problems have increased with the introduction of nutrient removal in many countries, and presently, there is no reliable control strategy for M. parvicella. Little is known about the physiology of M. parvicella, and conflicting data exist about its preferred organic substrates, and whether it is able to be physiologically active under anaerobic and anoxic conditions. In this study, the ability of M. parvicella to take up various radioactively labeled organic compounds was investigated in situ at three nutrient removal plants using a microautoradiographic technique. Of 12 compounds tested under aerobic conditions only the long chain fatty acids (LCFA), oleic acid and palmitic acid, and to some extent a lipid, trioleic acid, were assimilated. None of the simple substrates such as acetate, propionate, butyrate, glucose, ethanol, glycine and leucine were taken up. Furthermore, the uptake of oleic acid was compared under anaerobic, anoxic and aerobic conditions, and it was demonstrated that in addition to aerobic conditions M. parvicella was also able to take up oleic acid under anaerobic and anoxic conditions. No difference in substrate uptake pattern for M. parvicella was found among the tested activated sludge plants. The results strongly indicate that a better control strategy against M. parvicella must rely on a better understanding of presence and availability of triglycerides and LCFA, and an improved knowledge of the physiology of M. parvicella under anaerobic and anoxic conditions.

Effect of solids retention time on <i>Microthrix parvicella</i> growth

“…Continuous-flow experiments were conducted using primary effluent from MSTW supplemented with oleic acid in the form of Tween 80 to promote M. parvicella proliferation. The ability of long-chain fatty acids to stimulate the growth of M. parvicella is well documented for both activated sludge studies (Mamais et al, 1998;Andreasen and Nielsen., 1998) and pure cultures (Slijkhuis et al, 1984;Slijkhuis and Deinema, 1988). Activated sludge samples were periodically taken from the continuous-flow systems to conduct aerobic, and anoxic substrate uptake batch tests (OUR and NUR) as developed by Kristensen et al (1992).…”

Behavior of lipids in biological wastewater treatment processes

“…A detailed study to characterize the substrate uptake by filamentous bacteria was conducted by Andreasen and Nielsen [3,4]. They studied the ability of Microthrix parvicella, which is one of the filamentous bacteria responsible for bulking and foaming in many activated sludge treatment plants [5,87], to take up various organic compounds under aerobic, anaerobic and anoxic conditions.…”

“…Subsequently, under anaerobic conditions, PAO use the stored energy to take up organic substrates [99]. Therefore, the results reported by Andreasen and Nielsen [3,4] show that the presence of lipids (triacylglycerols and long-chain fatty acids) in wastewater promotes the growth of filamentous bacteria under aerobic, anaerobic or anoxic conditions. In accordance with Andreasen and Nielsen's [4] conclusion, a better control strategy against filamentous bacteria should include a better understanding of the behavior and effect of lipids on activated sludge.…”

Genome Sequence of “Candidatus Microthrix parvicella” Bio17-1, a Long-Chain-Fatty-Acid-Accumulating Filamentous Actinobacterium from a Biological Wastewater Treatment Plant

“…On culture media they grow meagerly, yet they seem to have an in situ competitive advantage mediated by their avid uptake of long-chain fatty acids, which are accumulated as neutral lipids under anaerobic conditions and converted into phospholipids for cell division under aerobic conditions (1,13).…”