Recent Advances and Future Prospects in Bacterial and Archaeal Locomotion and Signal Transduction

Abstract

The structure and function of two-component and chemotactic signaling and different aspects related to the motility of bacteria and archaea are key research areas in modern microbiology. Escherichia coli is the traditional model organism used to study chemotaxis signaling and motility. However, the recent study of a wide range of bacteria and even some archaea with different lifestyles has provided new insight into the ecophysiology of chemotaxis, which is essential for the establishment of different pathogens or beneficial bacteria in a host. The expanded range of model organisms has also permitted the study of chemosensory pathways unrelated to chemotaxis, multiple chemotaxis pathways within an organism, and new types of chemoreceptors. This research has greatly benefitted from technical advances in the field of cryomicroscopy, which continues to reveal with increasing resolution the complexity and diversity of large protein complexes like the flagellar motor or chemoreceptor arrays. In addition, sensitive instruments now allow an increasing number of experiments to be conducted at the single-cell level, thereby revealing information that is beginning to bridge the gap between individual cells and population behavior. Evidence has also accumulated showing that bacteria have evolved different mechanisms for surface sensing, which appears to be mediated by flagella and possibly type IV pili, and that the downstream signaling involves chemosensory pathways and two-component-system-based processes. Herein, we summarize the recent advances and research tendencies in this field as presented at the latest Bacterial Locomotion and Signal Transduction (BLAST XIV) conference.KEYWORDS chemotaxis, flagella, flagellar motility, signal transduction, two-component regulatory systems T he capacity to sense and respond to changes in environmental cues is an essential feature of the prokaryotic lifestyle. As a consequence, bacteria and archaea have evolved an array of different molecular mechanisms that permit the detection of signals in order to generate appropriate cellular responses. These responses are mediated primarily by one-and two-component systems, as well as chemosensory signaling pathways (1-4). Whereas the former systems mediate changes primarily at the transcriptional level, chemosensory pathways form the basis for chemotaxis, the directed movement of prokaryotes in compound gradients. The study of signaling processes is not only of fundamental interest but may also contribute to the tackling of one of the central clinical problems, which is the increasing amount of antibiotic-resistant pathogens. There is now a significant amount of data indicating that interference with signal transduction systems, motility, and chemotaxis can be an alternative strategy to weaken or block pathogens (5, 6).In

Recognition of dominant attractants by key chemoreceptors mediates recruitment of plant growth‐promoting rhizobacteria

“…Further examples illustrate that several of the other key attractants (fumaric and gluconic acids, Lys, Ser and Ala) that were identified in exudates of Cicer arietinum L., tomato and alfalfa, were also important attractants for rhizospheric microorganisms (Gitte et al, ; de Weert et al, ; Gupta Sood, ; Glekas et al, ; Webb et al, ). It appears that organic acids (especially the tricarboxylic acid cycle intermediates) and amino acids serve frequently as chemoattractants for various rhizobacteria (Bardy et al, ). Interestingly, citric acid, the most abundant compound in cucumber root exudates as well as in root exudates of tomato and sweet pepper (Kamilova et al, ), failed to induce chemotaxis of SQR9 even at 1000× concentrations (Fig.…”

“…Whereas some of these microorganisms are plant pathogens, others are plant growth-promoting rhizobacteria (PGPR) with the capacity to enhance plant growth by increasing nutrient acquisition, altering hormone levels or by suppressing plant pathogens (Lugtenberg and Kamilova, 2009). Plants recruit PGPRs to the rhizosphere by the release of specific signal molecules (Berendsen et al, 2012;Bardy et al, 2017). Bacterial chemotaxis is the capacity of directed swimming along a signal gradient (Bi and Sourjik, 2018).…”

Sensory Repertoire of Bacterial Chemoreceptors

“…Escherichia coli and Salmonella enterica serovar Typhimurium are the classic model organisms to study chemoreceptor-based signaling, but a variety of other species were studied in this respect, primarily during the last decade (23). E. coli has five chemoreceptors that funnel stimuli into a single chemotaxis signaling cascade (8).…”

High-Affinity Chemotaxis to Histamine Mediated by the TlpQ Chemoreceptor of the Human Pathogen Pseudomonas aeruginosa

“…More recently, chemoreceptor-based signaling has been studied in an array of bacteria with different lifestyles ( 9 ). The existing data suggest that the typical number of chemoreceptor genes in bacteria, which can reach as high as 80, is much higher than in E. coli ( 10 ).…”