Experimental and simulation analysis of community structure of nitrifying bacteria in a membrane-aerated biofilm

Abstract

Until now, only few attempts have been made to assess biofilm models simulating microenvironments in a biofilm. As a first step, we compare the microenvironment observed in a membrane aerated biofilm (MAB) to that derived from a two-dimensional computational model with individual ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) embedded in a continuum EPS matrix. Gradients of oxygen were determined by means of microelectrodes. The change in nitrifying bacterial populations with the biofilm depth was quantified using fluorescence in situ hybridization (FISH) in combination with a confocal laser scanning microscopy (CLSM). Microelectrode measurements revealed that oxic and anoxic or anaerobic regions exist within the MAB. The oxygen profile predicted by the model showed good agreement with that obtained by microelectrode measurements. The oxic part of the biofilm was dominated by NSO190 probe-hybridized AOB, which formed relatively large clusters of cells directly on the membrane surface, and by the NOB belonging to genus Nitrobacter sp. On the other hand, NOB belonging to genus Nitrospira sp. were abundant at the oxic-anoxic interface. The model prediction regarding AOB and Nitrobacter sp. distribution was consistent with the experimental counterpart. Measurements of AOB cluster size distribution showed that colonies are slightly larger adjacent to the membrane than at the inner part of the biofilm. The sizes predicted by the current model are larger than those obtained in the experiment, leading to the arguments that some factors not contained in the model would affect the cluster size.

Microbial Population Dynamics and Community Structure during the Formation of Nitrifying Granules to Treat Ammonia-Rich Inorganic Wastewater

“…The granule samples were fixed with a freshly prepared solution of 4% (w/v) paraformaldehyde for 18 h at 4°C (26). They were washed twice with phosphate-buffered saline (PBS) and subsequently dispersed using an ultrasonic homogenizer for analysis of the population dynamics.…”

Is gas-discharge plasma a new solution to the old problem of biofilm inactivation?

“…In some cases, this process results in the development of a mature biofilm, in which cells cluster in pillar-and mushroom-like structures with water channels between them, forming a primitive circulatory system (Kolter & Losick, 1998). In other cases, more compact, flat and homogeneous biofilm layers (Heydorn et al, 2000;Picioreanu et al, 2000), spherical clusters (Matsumoto et al, 2007), discrete microcolony structures (Massol-Deyá et al, 1995), ball-shaped microcolonies (Tolker-Nielsen et al, 2000) and honeycomb-like structures (Marsh et al, 2003;Russo et al, 2006) have been reported. Although it is out of the scope of this paper to extensively review the different biofilm structures reported, it is generally accepted that biofilms are not a continuous monolayer surface deposit but instead a thin base film, ranging from a patchy monolayer of cells to a film several layers thick (Stoodley et al, 1997).…”

Model‐based comparative performance analysis of membrane aerated biofilm reactor configurations

“…Multispecies 1-dimensional modeling has also been examined by Shanahan and Semmens (2004) and Terada et al (2007). A recent development has been the application of spatially structured biofilm modeling to the MABR (Matsumoto et al, 2007). This approach can be useful in the analysis of structure-function relationship and the spatial dynamics of microbial populations in stratified biofilms.…”