MDPI - Publisher of Open Access Journals

12 pages, 1137 KiB

Open AccessReview

Deciphering Bacterial Chemorepulsion: The Complex Response of Microbes to Environmental Stimuli

by Ruixin Fu and Haichao Feng

Microorganisms 2024, 12(8), 1706; https://doi.org/10.3390/microorganisms12081706 - 18 Aug 2024

Cited by 3 | Viewed by 2061

Bacterial motility relying on flagella is characterized by several modes, including swimming, swarming, twitching, and gliding. This motility allows bacteria to adapt remarkably well to hostile environments. More than 50% of bacteria naturally contain flagella, which are crucial for bacterial chemotaxis motility. Chemotaxis can be either positive, where bacteria move towards a chemical source, or negative, known as chemorepulsion, where bacteria move away from the source. Although much is known about the mechanisms driving chemotaxis towards attractants, the molecular mechanisms underlying chemorepulsion remain elusive. Chemotaxis plays an important role in the colonization of the rhizosphere by rhizobacteria. Recently, researchers have systematically studied the identification and recognition mechanisms of chemoattractants. However, the mechanisms underlying chemorepellents remain unclear. Systematically sorting and analyzing research on chemorepellents could significantly enhance our understanding of how these compounds help probiotics evade harmful environments or drive away pathogens. Full article

(This article belongs to the Special Issue Bacterial Communication)

► Show Figures

Figure 1

17 pages, 1697 KiB

Open AccessArticle

Chemotactic Responses of Xanthomonas with Different Host Ranges

by Marta Sena-Vélez, Elisa Ferragud, Cristina Redondo, James H. Graham and Jaime Cubero

Microorganisms 2023, 11(1), 43; https://doi.org/10.3390/microorganisms11010043 - 22 Dec 2022

Cited by 3 | Viewed by 2273

Abstract

Xanthomonas citri pv. citri (Xcc) (X. citri subsp. citri) type A is the causal agent of citrus bacterial canker (CBC) on most Citrus spp. and close relatives. Two narrow-host-range strains of Xcc, A^w and A*, from Florida and Southwest Asia, respectively, infect only Mexican lime (Citrus aurantifolia) and alemow (C. macrophylla). In the initial stage of infection, these xanthomonads enter via stomata to reach the apoplast. Herein, we investigated the differences in chemotactic responses for wide and narrow-host-range strains of Xcc A, X. euvesicatoria pv. citrumelonis (X. alfalfae subsp. citrumelonis), the causal agent of citrus bacterial spot, and X. campestris pv. campestris, the crucifer black rot pathogen. These strains of Xanthomonas were compared for carbon source use, the chemotactic responses toward carbon compounds, chemotaxis sensor content, and responses to apoplastic fluids from Citrus spp. and Chinese cabbage (Brassica pekinensis). Different chemotactic responses occurred for carbon sources and apoplastic fluids, depending on the Xanthomonas strain and the host plant from which the apoplastic fluid was derived. Differential chemotactic responses to carbon sources and citrus apoplasts suggest that these Xanthomonas strains sense host-specific signals that facilitate their location and entry of stomatal openings or wounds. Full article

(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)

► Show Figures

Figure 1

12 pages, 1923 KiB

Open AccessArticle

PAS Domain-Containing Chemoreceptors Influence the Signal Sensing and Intestinal Colonization of Vibrio cholerae

by Rundong Shu, Chaoqun Yuan, Bojun Liu, Yang Song, Leqi Hou, Panpan Ren, Hui Wang and Chunhong Cui

Genes 2022, 13(12), 2224; https://doi.org/10.3390/genes13122224 - 27 Nov 2022

Cited by 2 | Viewed by 1899

Abstract

Bacterial chemotaxis is the phenomenon in which bacteria migrate toward a more favorable niche in response to chemical cues in the environment. The methyl-accepting chemotaxis proteins (MCPs) are the principal sensory receptors of the bacterial chemotaxis system. Aerotaxis is a special form of chemotaxis in which oxygen serves as the signaling molecule; the process is dependent on the aerotaxis receptors (Aer) containing the Per-Arnt-Sim (PAS) domain. Over 40 MCPs are annotated on the genome of Vibrio cholerae; however, little is known about their functions. We investigated six MCPs containing the PAS domain in V. cholerae El Tor C6706, namely aer2, aer3, aer4, aer5, aer6, and aer7. Deletion analyses of each aer homolog gene indicated that these Aer receptors are involved in aerotaxis, chemotaxis, biofilm formation, and intestinal colonization. Swarming motility assay indicated that the aer2 gene was responsible for sensing the oxygen gradient independent of the other five homologs. When bile salts and mucin were used as chemoattractants, each Aer receptor influenced the chemotaxis differently. Biofilm formation was enhanced by overexpression of the aer6 and aer7 genes. Moreover, deletion of the aer2 gene resulted in better bacterial colonization of the mutant in adult mice; however, virulence gene expression was unaffected. These data suggest distinct roles for different Aer homologs in V. cholerae physiology. Full article

(This article belongs to the Special Issue Microbe-Host Interaction)

► Show Figures

Figure 1

15 pages, 2299 KiB

Open AccessArticle

The Only Chemoreceptor Encoded by che Operon Affects the Chemotactic Response of Agrobacterium to Various Chemoeffectors

by Jingyang Ye, Miaomiao Gao, Qingxuan Zhou, Hao Wang, Nan Xu and Minliang Guo

Microorganisms 2021, 9(9), 1923; https://doi.org/10.3390/microorganisms9091923 - 10 Sep 2021

Cited by 7 | Viewed by 3152

Abstract

Chemoreceptor (also called methyl-accepting chemotaxis protein, MCP) is the leading signal protein in the chemotaxis signaling pathway. MCP senses and binds chemoeffectors, specifically, and transmits the sensed signal to downstream proteins of the chemotaxis signaling system. The genome of Agrobacterium fabrum (previously, tumefaciens) C58 predicts that a total of 20 genes can encode MCP, but only the MCP-encoding gene atu0514 is located inside the che operon. Hence, the identification of the exact function of atu0514-encoding chemoreceptor (here, named as MCP₅₁₄) will be very important for us to understand more deeply the chemotaxis signal transduction mechanism of A. fabrum. The deletion of atu0514 significantly decreased the chemotactic migration of A. fabrum in a swim plate. The test of atu0514-deletion mutant (Δ514) chemotaxis toward single chemicals showed that the deficiency of MCP₅₁₄ significantly weakened the chemotactic response of A. fabrum to four various chemicals, sucrose, valine, citric acid and acetosyringone (AS), but did not completely abolish the chemotactic response. MCP₅₁₄ was localized at cell poles although it lacks a transmembrane (TM) region and is predicted to be a cytoplasmic chemoreceptor. The replacement of residue Phe328 showed that the helical structure in the hairpin subdomain of MCP₅₁₄ is a direct determinant for the cellular localization of MCP₅₁₄. Single respective replacements of key residues indicated that residues Asn336 and Val353 play a key role in maintaining the chemotactic function of MCP₅₁₄. Full article

(This article belongs to the Special Issue Molecular Analysis of Plant Pathogenic Bacteria)

► Show Figures

Figure 1

26 pages, 6097 KiB

Open AccessReview

Multistep Signaling in Nature: A Close-Up of Geobacter Chemotaxis Sensing

by Marta A. Silva and Carlos A. Salgueiro

Int. J. Mol. Sci. 2021, 22(16), 9034; https://doi.org/10.3390/ijms22169034 - 21 Aug 2021

Cited by 4 | Viewed by 3873

Abstract

Environmental changes trigger the continuous adaptation of bacteria to ensure their survival. This is possible through a variety of signal transduction pathways involving chemoreceptors known as methyl-accepting chemotaxis proteins (MCP) that allow the microorganisms to redirect their mobility towards favorable environments. MCP are two-component regulatory (or signal transduction) systems (TCS) formed by a sensor and a response regulator domain. These domains synchronize transient protein phosphorylation and dephosphorylation events to convert the stimuli into an appropriate cellular response. In this review, the variability of TCS domains and the most common signaling mechanisms are highlighted. This is followed by the description of the overall cellular topology, classification and mechanisms of MCP. Finally, the structural and functional properties of a new family of MCP found in Geobacter sulfurreducens are revisited. This bacterium has a diverse repertoire of chemosensory systems, which represents a striking example of a survival mechanism in challenging environments. Two G. sulfurreducens MCP—GSU0582 and GSU0935—are members of a new family of chemotaxis sensor proteins containing a periplasmic PAS-like sensor domain with a c-type heme. Interestingly, the cellular location of this domain opens new routes to the understanding of the redox potential sensing signaling transduction pathways. Full article

(This article belongs to the Special Issue Bacterial Chemoreceptors and Chemosensory Pathways)

► Show Figures

Figure 1

14 pages, 1284 KiB

Open AccessReview

Chemotaxis of Beneficial Rhizobacteria to Root Exudates: The First Step towards Root–Microbe Rhizosphere Interactions

by Haichao Feng, Ruixin Fu, Xueqin Hou, Yu Lv, Nan Zhang, Yunpeng Liu, Zhihui Xu, Youzhi Miao, Tino Krell, Qirong Shen and Ruifu Zhang

Int. J. Mol. Sci. 2021, 22(13), 6655; https://doi.org/10.3390/ijms22136655 - 22 Jun 2021

Cited by 154 | Viewed by 9440

Abstract

Chemotaxis, the ability of motile bacteria to direct their movement in gradients of attractants and repellents, plays an important role during the rhizosphere colonization by rhizobacteria. The rhizosphere is a unique niche for plant–microbe interactions. Root exudates are highly complex mixtures of chemoeffectors composed of hundreds of different compounds. Chemotaxis towards root exudates initiates rhizobacteria recruitment and the establishment of bacteria–root interactions. Over the last years, important progress has been made in the identification of root exudate components that play key roles in the colonization process, as well as in the identification of the cognate chemoreceptors. In the first part of this review, we summarized the roles of representative chemoeffectors that induce chemotaxis in typical rhizobacteria and discussed the structure and function of rhizobacterial chemoreceptors. In the second part we reviewed findings on how rhizobacterial chemotaxis and other root–microbe interactions promote the establishment of beneficial rhizobacteria-plant interactions leading to plant growth promotion and protection of plant health. In the last part we identified the existing gaps in the knowledge and discussed future research efforts that are necessary to close them. Full article

(This article belongs to the Special Issue Bacterial Chemoreceptors and Chemosensory Pathways)

► Show Figures

Figure 1

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI