Microorganisms

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Dr. Annabelle Merieau

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Guest Editor

1. Laboratory of Microbiology Signals and Microenvironment (LMSM EA 4312), University of Rouen Normandy, F-27000 Evreux, France
2. Research Federations NORVEGE Fed4277 & NORSEVE, Normandy University, F-76821 Mont-Saint-Aignan, France
Interests: epigenetics; adaptation; pathogens; cytotoxicity; bacterial secretion systems; Pseudomonas fluorescens

Special Issue Information

Dear Colleagues,

The fabulous adaptability of bacteria is attributable in large part to their ability to communicate with each other as well as with their environment. In response to abiotic, eukaryotic or prokaryotic stimuli, bacteria emit responses to coordinate and modulate their behaviour. This dialog is essential to preserve their niches or to conquer new habitats. Understanding the mechanisms of bacterial communication is therefore one of the major issues in microbiology. Indeed, knowledge on the mechanisms related to signal perception or emission by bacteria is a prerequisite for the optimisation of future biocontrol strategies.

This Special Issue of Microorganisms welcomes researchers to contribute research articles, reviews and opinions addressing the latest knowledge on interbacterial communication, quorum sensing, and plant–bacteria or animal cell–bacteria interactions, both in fundamental research and its applications.

Dr. Annabelle Merieau
Guest Editor

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Published Papers (2 papers)

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20 pages, 3302 KiB

Open AccessArticle

Unraveling the Intertwined Effect of pH on Helicobacter pylori Motility and the Microrheology of the Mucin-Based Medium It Swims in

by Clover Su-Arcaro, Wentian Liao, Katarzyna Bieniek, Maira A. Constantino, Savannah M. Decker, Bradley S. Turner and Rama Bansil

Microorganisms 2023, 11(11), 2745; https://doi.org/10.3390/microorganisms11112745 - 10 Nov 2023

Viewed by 1498

Abstract

The gastric pathogen, Helicobacter pylori bacteria have to swim across a pH gradient from 2 to 7 in the mucus layer to colonize the gastric epithelium. Previous studies from our group have shown that porcine gastric mucin (PGM) gels at an acidic pH < 4, and H. pylori bacteria are unable to swim in the gel, although their flagella rotate. Changing pH impacts both the rheological properties of gastric mucin and also influences the proton (H+)-pumped flagellar motors of H. pylori as well as their anti-pH sensing receptors. To unravel these intertwined effects of acidic pH on both the viscoelastic properties of the mucin-based mucus as well as the flagellar motors and chemo-receptors of the bacterium, we compared the motility of H. pylori in PGM with that in Brucella broth (BB10) at different pH values using phase contrast microscopy to track the motion of the bacteria. The results show that the distribution of swimming speeds and other characteristics of the bacteria trajectories exhibit pH-dependent differences in both media. The swimming speed exhibits a peak at pH 4 in BB10, and a less pronounced peak at a higher pH of 5 in PGM. At all pH values, the bacteria swam faster and had a longer net displacement in BB10 compared to PGM. While the bacteria were stuck in PGM gels at pH < 4, they swam at these acidic pH values in BB10, although with reduced speed. Decreasing pH leads to a decreased fraction of motile bacteria, with a decreased contribution of the faster swimmers to the distributions of speeds and net displacement of trajectories. The body rotation rate is weakly dependent on pH in BB10, whereas in PGM bacteria that are immobilized in the low pH gel are capable of mechano-sensing and rotate faster. Bacteria can be stuck in the gel in various ways, including the flagella getting entangled in the fibers of the gel or the cell body being stuck to the gel. Our results show that in BB10, swimming is optimized at pH4, reflecting the combined effects of pH sensing by anti-pH tactic receptors and impact on H+ pumping of flagellar motors, while the increase in viscosity of PGM with decreasing pH and gelation below pH 4 lead to further reduction in swimming speed, with optimal swimming at pH 5 and immobilization of bacteria below pH 4. Full article

(This article belongs to the Special Issue Bacterial Communication)

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17 pages, 4773 KiB

Open AccessArticle

The Deciphering of Growth-Dependent Strategies for Quorum-Sensing Networks in Pseudomonas aeruginosa

by Tereza Juříková, Hynek Mácha, Vanda Lupjanová, Tomáš Pluháček, Helena Marešová, Barbora Papoušková, Dominika Luptáková, Rutuja H. Patil, Oldřich Benada, Michal Grulich and Andrea Palyzová

Microorganisms 2023, 11(9), 2329; https://doi.org/10.3390/microorganisms11092329 - 15 Sep 2023

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Abstract

Pseudomonas aeruginosa is recognized as a significant cause of morbidity and mortality among nosocomial pathogens. In respiratory infections, P. aeruginosa acts not only as a single player but also collaborates with the opportunistic fungal pathogen Aspergillus fumigatus. This study introduced a QS molecule portfolio as a potential new biomarker that affects the secretion of virulence factors and biofilm formation. The quantitative levels of QS molecules, including 3-o-C12-HSL, 3-o-C8-HSL, C4-HSL, C6-HSL, HHQ, PQS, and PYO, measured using mass spectrometry in a monoculture, indicated metabolic changes during the transition from planktonic to sessile cells. In the co-cultures with A. fumigatus, the profile of abundant QS molecules was reduced to 3-o-C12-HSL, C4-HSL, PQS, and PYO. A decrease in C4-HSL by 50% to 170.6 ± 11.8 ng/mL and an increase 3-o-C12-HSL by 30% up to 784.4 ± 0.6 ng/mL were detected at the stage of the coverage of the hyphae with bacteria. Using scanning electron microscopy, we showed the morphological stages of the P. aeruginosa biofilm, such as cell aggregates, maturated biofilm, and cell dispersion. qPCR quantification of the genome equivalents of both microorganisms suggested that they exhibited an interplay strategy rather than antagonism. This is the first study demonstrating the quantitative growth-dependent appearance of QS molecule secretion in a monoculture of P. aeruginosa and a co-culture with A. fumigatus. Full article

(This article belongs to the Special Issue Bacterial Communication)

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