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Microbial biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Capsules or slime layers are produced by many bacteria to surround their cells and vary in structural complexity, ranging from a disorganized slime layer of extracellular polymer to a highly structured capsule or glycocalyx. These structures can protect cells from engulfment by eukaryotic cells, such as macrophages. They can also act as antigens and be involved in cell recognition, as well as aiding attachment to surfaces and the formation of biofilms. The assembly of these extracellular structures is dependent on bacterial secretion systems. These transfer proteins from the cytoplasm into the periplasm or into the environment around the cell. Many types of secretion systems are known, and as these structures are often essential for the virulence of pathogens, they are intensively studied. Certain genera of Gram-positive bacteria, such as Bacillus, Clostridium, Sporohalobacter, Anaerobacter, and Heliobacterium, can form highly resistant, dormant structures called endospores. In almost all cases, one endospore is formed and this is not a reproductive process, although Anaerobacter can make up to seven endospores in a single cell. Endospores have a central core of cytoplasm containing DNA and ribosomes, surrounded by a cortex layer and protected by an impermeable and rigid coat.
Comparative Study of Predictive Models in Microbial-Induced Corrosion
Published in Shampa Sen, Leonid Datta, Sayak Mitra, Machine Learning and IoT, 2018
Matrix layers are formed when bacterial species colonize a particular substrate and start the secretion of Extra cellular Polymeric Substances (EPS) (Beech and Sunner 2004), leading to the onset of corrosion (Alabbas et al. 2013). The EPS, along with the microbial colonies, constitute the biofilm commonly called “slime layer.” The EPS layer are commonly composed of minor concentrations of lipids and nucleic acids engulfed in ploysaccharides and protiens. Formed as a monolayer in the initial stages, these have a potential of increasing their thickness up to several centimeters and tend to be highly hydrated (∼97% water). One of the primary characteristics of biofilm is the exponential rate of bacterial cell growth exhibited; with the cell count in the colonies reaching as high as Log10 (6.0) cells/cm2 (Bouman et al., 1982) thereby establishing synergistic communities commonly known as “Microconsortia.” Another prominent characteristic is the free motility of the bacteria within the EPS layer, resulting in pronounced pH gradient across the matrix (Figure 6.1) (Gu 2012).
Phosphate removal in seawater reverse osmosis feed water: An option to control biofouling
Published in Nirajan Dhakal, Controlling Biofouling in Seawater Reverse Osmosis Membrane Systems, 2017
Bacterial colonization, growth, and biofilm formation: the primary colonization starts when the bacteria that primarily adhere to the membrane surface grow at the expense of available nutrients. The number of bacterial colonies and the production of EPS increases when more bacteria of different species adhere to the membrane surface, which leads to the formation of slime layer and is known as a biofilm.
Mechanisms and efficacy of disinfection in ceramic water filters: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2021
Within CWF research, the traditional understanding of the silver’s effectiveness has been based largely on studies such as Oyanedel-Craver and Smith (2008), where after 75–85 min of filtration, filters painted with, and submerged in, a 600 mg/L colloidal silver solution yielded LRVs of 6 and 6.5, respectively, whereas filters without any silver yielded LRVs of 4.6 and 5.5 (Oyanedel-Craver & Smith, 2008). And because of findings like these, Potters-for-Peace (PfP; the largest organization in this domain) states that “Silver is applied to the filter to achieve two objectives: (1) to take advantage of the bactericidal quality of silver in the purification of water as it is filtered; and (2) to prevent the growth of the “slime layer” of bacteria that can form on the filter wall” (p. 91) (Ceramics Manufacturing Working Group, 2010). This section therefore addresses both of these assertations, beginning with the latter.
Domestic wastewater treatment efficiency of the pilot-scale trickling biofilter system with variable flow rates and hydraulic retention times
Published in Environmental Technology, 2021
Abdul Rehman, Haris Ali, Iffat Naz, Devendra P. Saroj, Safia Ahmed
In this study, bacteriological analysis of biofilm developed on pebbles and gravels filter bed was performed by pure culture technique and seven different bacterial isolates were identified from the slime layer. Out of seven different bacterial isolates, five were Gram negative and two were Gram positive. After microscopy, these bacterial isolates were subcultured on nutrient agar media plates and different cultural characteristics were observed. After cultural characteristics, a complete identification of these bacterial isolates was carried out by performing different biochemical tests. The detailed description of microscopy, cultural and biochemical analysis of all identified bacterial isolates is given in Table 3. Anderson et al. [34] studied the biofilm formation process of 13 different bacterial species in attached growth system during wastewater treatment. About 9 pure cultures of bacteria were used for the formation of biofilm in TF by Butterfield and Wattie [35] and above 200 different species including bacteria, protozoa, fungi, algae, worms and insects were used for the development of biofilm on a suitable media in TF by Cooke [36].
Effects of zinc oxide nanoparticles on sludge anaerobic fermentation: phenomenon and mechanism
Published in Journal of Environmental Science and Health, Part A, 2020
Baodan Jin, Yue Yuan, Ping Zhou, Jiahui Niu, Jintao Niu, Jingwen Dai, Nuonan Li, Hongfan Tao, Zhigang Ma, Ju Zhang, Zhongfang Zhang, Yu Li
Three layers were separated from WAS flocs: tightly bound extracellular polymeric substance (TB-EPS), loosely bound EPS (LB-EPS) and the outer slime layer (SB-EPS) from inside to outside of the cell. The extraction method has been described in a previous report.[22] The detection method was the same as that for proteins and polysaccharides.[16]