Microbial Biofilms
Chaminda Jayampath Seneviratne in Microbial Biofilms, 2017
Dispersal is the least understood and perhaps the most complicated process in both fungal and bacterial biofilm development. The trigger for the dispersal process to occur and the biological pathways modulating dispersal may vary considerably among different microorganisms [41]. Cells from the biofilm may detach singly or as a group and move through a fluid phase to seed new sites. Numerous research groups have put forth efforts to understand this mechanism in pathogenic organisms such as P. aeruginosa and C. albicans. Bacterial secondary messengers such as cyclic di-GMP have been shown to provide critical signals for biofilm formation as well as dispersal [42]. The factors which signal dispersion can vary, ranging from environmental stimuli, nutrients, certain chemicals such as cis-2-decenoic acid or nitric oxide or proteins such as BdlA, a chemotaxis regulator [43–45]. It has also been shown recently that phosphorylation status of diguanylate cyclase NIcD can affect the dispersal of biofilms in P. aeruginosa [46]. The aforementioned study demonstrated dispersal inducing environmental cues are sensed by the diguanylate cyclase NicD belonging to a seven transmembrane receptor family. The sensing of dispersal cues by NicD results in NicD dephosphorylation, followed by activation of a chemotaxis regulator BdlA, which in turn activates DipA, a phosphodiesterase molecule. This leads to altered levels of second messenger cyclic-di-GMP molecules signalling dispersion. Studies on C. albicans biofilms have found Set3–NRG1 complex as possible regulators of biofilm dispersal. Set3, an NAD-dependent histone deacetylation complex, modulates NRG, a transcriptional regulator of biofilm dispersal and a repressor of filamentation [47]. The typical dispersal of C. albicans from biofilms is in the yeast form [48]. Moreover, it was shown that deletion of Nrg1 gene in C. albicans attenuates in vivo virulence of the fungus in systemic candidiasis [49]. Therefore, with proper understanding of the dispersal process, alternative therapeutic strategies may be devised for controlling the spread of these pathogenic organisms.
Bacterial biofilm-derived antigens: a new strategy for vaccine development against infectious diseases
Published in Expert Review of Vaccines, 2021
Abraham Loera-Muro, Alma Guerrero-Barrera, Yannick Tremblay D.N., Skander Hathroubi, Carlos Angulo
Some signaling molecules can be used by bacteria for intra-species and inter-species communications. One of these molecules is the second messenger, cyclic di-GMP (c-di-GMP). In bacteria, c-di-GMP promotes the switch between lifestyles: a sedentary biofilm or a motile free-floating lifestyle [52]. It also affects a wide range of bacterial behaviors, including the cell cycle, motility, fimbrial synthesis, type III secretion, modulation of RNA, stress response, bacterial predation, and virulence [53]. Diguanylate cyclases have a GGDEF domain that generates c-di-GMP from two GTP molecules, whereas phosphodiesterases have a EAL or HD-GYP domain that degrades c-di-GMP to pGpG [54]. Specific c-di-GMP receptor proteins or riboswitch RNAs sense the changes in c-di-GMP levels and regulate specific processes resulting in different phenotypes [53]. Higher diguanylate cyclase activity increases intracellular c-di-GMP levels that stimulate the production of various adhesins and biofilm-associated matrix components resulting in increased adhesion and biofilm formation [52]. On the opposite spectrum, high phosphodiesterase activity reduces the levels of c-di-GMP, which suppresses adhesion leading to biofilm dispersion [54]. For example, Legionella pneumophila, an opportunistic pathogen, uses the second messenger c-di-GMP to regulate an array of bacterial processes that include motility, cell division, differentiation, virulence, as well as biofilm formation [55,56].
Impact of sodium nitroprusside concentration added to batch cultures of Escherichia coli biofilms on the c-di-GMP levels, morphologies and adhesion of biofilm-dispersed cells
Published in Biofouling, 2022
Ayse Ordek, F. Pinar Gordesli-Duatepe
Previously, Kim and Harshey (2016) reported that diguanylate cyclase (DGC) YfiN protein associated with intracellular c-di-GMP production acts as a division inhibitor in response to cell-envelope stress in E. coli. After the cell expands to divide, it was shown that YfiN settles in the localization area of division proteins and arrests the division process, and the inhibition of the assembly of division proteins causes an increase in bacterial cell size (Weart et al. 2007). In addition, it was also reported that high intracellular c-di-GMP levels are required for mid-cell localization of YfiN in E. coli. Likewise, Schäper et al. (2016) reported that high c-di-GMP levels provoked Sinorhizobium meliloti cell elongation, and the highest c-di-GMP content resulted in the strongest cell elongation. Since the presence of SNP in the medium results in the formation of NO and other RNS which can lead to an increase in the intracellular c-di-GMP level and a possible disruption of the cell envelope by inducing oxidative and/or nitrosative stresses, the observed increase in the length and width of the dispersed cells compared to those of planktonic cells might have been related to the level of their c-di-GMP content together with the degree of envelope stress experienced by the cells.
Synthesis, antimicrobial, anti-biofilm evaluation, and molecular modelling study of new chalcone linked amines derivatives
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Shahenda M. El-Messery, El-Sayed E. Habib, Sarah T. A. Al-Rashood, Ghada S. Hassan
The second messenger cyclic di-GMP (c-di-GMP) has recently emerged as a novel signal that controls biofilm formation and represses motility. Synthesis of c-di-GMP occurs via diguanylate cyclase (DGC) enzymes encoding GGDEF domains, while degradation of c-di-GMP occurs via phosphodiesterase (PDE) enzymes6,7. Analysis of bacterial genome sequences revealed that enzymes predicted to synthesize or degrade c-diGMP are found in 85% of all bacteria, including many prominent human pathogens. Deletion of active DGCs completely abolishes biofilm formation, suggesting c-di-GMP is essential for this process in bacteria that utilize the signal8–11.
Related Knowledge Centers
- Catalysis
- Chemical Reaction
- Enzyme
- Molecule
- Pyrophosphate
- Substrate
- Guanosine Triphosphate
- Product
- Cyclic Di-Gmp
- Guanosine Monophosphate