In situ studies of the phylogeny and physiology of filamentous bacteria with attached growth

Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701. A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking. In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants. Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain. All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria , Firmicutes , Actinobacteria and Bacteroidetes , for which group-specific probes were used. The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system. Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes. However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse. The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors. It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria. No significant physiological differences were found between TM7-positive and TM7-negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested. These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions

Effect of Mixed-Species Biofilm on Copper Surfaces in Cooling Water System

This study aimed to investigate the formation and effect of a biofilm on copper heat exchangers in full-scale system conditions. A modified Pedersen device with copper coupons was installed in parallel to a heat exchanger system to investigate several physico-chemical parameters, such as bacterial enumeration, carbohydrate content of exopolymeric substances, weight loss of test/control coupons, Cu concentrations, and corrosion products over ten months. Findings of this study showed that planktonic bacterial cells attach to each other and form a mixed-species biofilm on the copper coupon surface even though copper is toxic to a variety of microorganisms. These results also revealed that the mixed-species biofilm has a corrosive effect on copper surfaces used in cooling water systems despite the presence of biocide and the corrosion inhibitor. Additionally, it was demonstrated that a shock-dosed biocide application increased the corrosion rate on copper surface in a real system. Preventing risk of microbiologically influenced corrosion entails appropriate material selection and proper/regular chemical treatment of cooling systems. The current study provides useful insights through the evaluation of corrosion of materials with microbiological techniques

Microbiome of Drinking Water Distribution Systems

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