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Bacterial Attachment and Biofilm Formation on Biomaterials
Published in Nihal Engin Vrana, Biomaterials and Immune Response, 2018
A more detailed description of the biofilm formation phases also takes into account biofilm topology and time evolution scale (Figure 5.1). For example [44], five biofilm phases have been described: the initial binding (adhesion) is stage I (attachment may still be reversible, as some cells can detach). Stage II starts when the adhesion becomes irreversible (some minutes after stage I). After the initial adhesion to the epithelial surface, the bacteria start to multiply while emitting chemical signals that inter-communicate between the bacterial cells – a process known as “quorum sensing”. Once the signal intensity exceeds a certain threshold, the genetic mechanisms underlying exopolysaccharide (EPS) production are activated, leading to the entrapment of nutrients and other planktonic bacteria [45]. During stage II, aggregates are formed and bacterial motility is decreased, forming progressively layered stacks of 10–50 μm (the biofilm stage III). When the biofilm reaches its ultimate thickness (generally > 100–150 μm), it goes into stage IV, indicating its maximal mechanical stability. During stage V, bacterial dispersion becomes notable as some bacteria return to the planktonic phenotype and leave the biofilm. This begins several days after stage IV [46].
Bacterial Chemotaxis, Current Knowledge and Future Need for Application in Hydrocarbon Remediation Technologies
Published in Wael Ahmed Ismail, Jonathan Van Hamme, Hydrocarbon Biotechnology, 2023
Nisenbaum Melina, Georgina Corti-Monzón, Silvia E. Murialdo
In recent years, chemotaxis studies with microfluidic techniques have greatly advanced. Compared to traditional detection methods, microfluidic assays may allow for manipulation and characterization of gradients with high accuracy (Ahmed et al., 2010), afford precise control over the bacterial microenvironment, increase detection sensitivity, and can be used qualitatively and quantitatively. With this technique, Stocker et al. (2008) demonstrated bacterial migration in response to different nutrients in a microfluidic device with environmentally realistic dimensions and dynamics. Classified into two categories, microfluidic devices are for either continuous flow or static diffusion assays. The continuous flow-based methods allow the user to generate different types of chemo-effector gradients using laminar flow and diffusion mixing (Englert et al., 2009; Jeong et al., 2010, 2013b; Si et al., 2012; Wu et al., 2013b). However, bacterial motility can be disturbed by shear forces induced by high flow (Marcos et al., 2012), requiring the use of external pumps and flow regulators. Diffusion-based methods provide chemical gradients without flow, require more time to deploy, but rely on less external equipment and do not interfere with bacterial motility. Recently, Jeong et al. (2013) presented a pump-less microfluidic device that solves the problem of slow diffusion of chemoeffectors and possibly the disturbance of bacterial motility driven by high flow rate. Microfluidic devices can provide a convenient tool for laboratory experiments and could play important roles in real applications in the near future (Zang et al., 2017).
Stimulated petroleum biodegradation
Published in J. van Eyk, Petroleum Bioventing, 1997
Finally, bacterial motility also appears to play a role in bacterial movement in porous subsurface formations (Reynolds 198926) i.e. motile strains penetrate sand-packed cores faster than non-motile strains.
Principles for quorum sensing-based exogeneous denitrifier enhancement of nitrogen removal in biofilm: a review
Published in Critical Reviews in Environmental Science and Technology, 2023
Ying-nan Zhu, Jinfeng Wang, Qiuju Liu, Ying Jin, Lili Ding, Hongqiang Ren
In addition, QS can modulate bacterial motility and chemotaxis to promote colonization and metabolization, thus rapidly and adequately degrading pollutants. Pili and flagella play important roles in motility, adhesion, and the uptake and emission of proteins and DNA, which can disassemble rapidly under certain environmental conditions (Craig et al., 2019). Chemotaxis is the broad ability of motile microorganisms to guide their movement along chemical gradients (Keegstra et al., 2022). In Azospirillum brasilense, chemotaxis can be mediated by two pathways: Che1 and Che4, which affects nitrogen metabolization (nitrate assimilation and nitrogen fixation), depending on the transcription regulation of global regulator rpoN (encoding RpoN) (Ganusova et al., 2021). Moreover, when the cells sense the carrier surface, the QS gene rhl is expressed, regulating the production of EPS and surfactants, controlling microbial chemotaxis through flagella, and forming biofilms (Saxena & Gupta, 2020).
Applications of bioremediation and phytoremediation in contaminated soils and waters: CREST publications during 2018–2022
Published in Critical Reviews in Environmental Science and Technology, 2023
Chen-Jing Liu, Song-Ge Deng, Chun-Yan Hu, Peng Gao, Eakalak Khan, Chang-Ping Yu, Lena Q. Ma
Biofilms are effective in nitrogen removal due to their advantages of high loading capacity and efficiency as well as their abilities to retain microorganisms with a promising regeneration (Zhu et al., 2022). Exogenous quorum sensing bacteria can efficiently promote the formation of biofilm by adhesion, growth, maturation, and diffusion, thus improving denitrification and nitrogen removal (Zhu et al., 2022). Besides, they proposed that the soluble signal molecules, such as acyl-homoserine-lactones, oligopeptide autoinducers, and hydroxyl-palmitic acid methyl ester, play important roles in regulating bacterial growth, metabolism, gene transcription, extracellular polymeric substance formation, bacterial motility, and community structure (Zhu et al., 2022). Hence, these signal molecules may help in controlling nitrogen removal efficiency.
Shift of microbial diversity and function in high-efficiency performance biotrickling filter for gaseous xylene treatment
Published in Journal of the Air & Waste Management Association, 2019
Mingxue Li, Yantao Shi, Yixuan Li, Yizhe Sun, Chunhui Song, Zhiyong Huang, Zongzheng Yang, Yifan Han
The PICRUSt analysis results obtained approximately 300 predicted functions, including transcription factors, ABC transporters, two-component systems, secretion systems, DNA repair and recombination proteins, etc. In addition to some general functional predictions, the overall data also demonstrated the great potential of the studied microbial community in the degradation of aromatics. Naphthalene degradation, toluene degradation, polycyclic aromatic hydrocarbon degradation, styrene degradation, ethylbenzene degradation, and xylene degradation were all predicted (Figure 7). The comprehensiveness of community functions indirectly explained the reasons for the good performance of the system. Cluster analysis indicated similar functional activity in the middle and bottom packing layers, which was consistent with the result of the middle and lower community structure similarity. Obviously, some cell basic functions, such as bacterial motility proteins, other ion-coupled transporters, and ribosome biogenesis, were different in each layer. Furthermore, the functions of chlorobenzene, nitrotoluene, and xylene degradation were more significant in the bottom packing layer. The reason for this result was directly associated with the dominant species in the bottom packing layer. Some strains of genera Pseudomonas, Rhodococcus, and Pandoraea have been reported to have xylene, nitrotoluene, and chlorobenzene degradation ability, respectively (Baptista et al. 2010; Jeong, Hirai, and Shoda 2009; Kundu, Hazra, and Chaudhari 2016).