Tetrahymena thermophila Predation Enhances Environmental Adaptation of the Carp Pathogenic Strain Aeromonas hydrophila NJ-35

Abstract

Persistence of Aeromonas hydrophila in aquatic environments is the principle cause of fish hemorrhagic septicemia. Protistan predation has been considered to be a strong driving force for the evolution of bacterial defense strategies. In this study, we investigated the adaptive traits of A. hydrophila NJ-35, a carp pathogenic strain, in response to Tetrahymena thermophila predation. After subculturing with Tetrahymena, over 70% of A. hydrophila colonies were small colony variants (SCVs). The SCVs displayed enhanced biofilm formation, adhesion, fitness, and resistance to bacteriophage infection and oxidative stress as compared to the non-Tetrahymena-exposed strains. In contrast, the SCVs exhibited decreased intracellular bacterial number in RAW264.7 macrophages and were highly attenuated for virulence in zebrafish. Considering the outer membrane proteins (OMPs) are directly involved in bacterial interaction with the external surroundings, we investigated the roles of OMPs in the antipredator fitness behaviors of A. hydrophila. A total of 38 differentially expressed proteins were identified in the SCVs by quantitative proteomics. Among them, three lipoproteins including SurA, Slp, and LpoB, and a serine/threonine protein kinase (Stpk) were evidenced to be associated with environmental adaptation of the SCVs. Also, the three lipoproteins were involved in attenuated virulence of SCVs through the proinflammatory immune response mediated by TLR2. This study provides an important contribution to the understanding of the defensive traits of A. hydrophila against protistan predators.

VscF in T3SS1 Helps to Translocate VPA0226 in Vibrio parahaemolyticus

“…Escherichia coli SM10λpir strains were used for the general manipulation and mobilization of plasmids into V. parahaemolyticus via conjugation ( Miller and Mekalanos, 1988 ). The pMMB207 shuttle plasmid was used as an overexpression plasmid ( Liu et al, 2018 ). Thiosulfate citrate bile salts sucrose (TCBS) agar was used to screen mutant and complementation strains containing chloramphenicol ( Orkin, 1990 ).…”

“…Cytotoxicity was assessed via morphology and the release of lactate dehydrogenase (LDH) using an LDH Cytotoxicity Assay Kit (Beyotime, C0016) ( Liu et al, 2018 ). First, HeLa cells were infected with WT POR-1, Δ vscF , and CΔ vscF for 3 h with 5% CO 2 at a multiplicity of infection (MOI) of 10 in DMEM supplemented with 1% FBS ( Kodama et al, 2007 ), washed three times with sterile phosphate buffered saline (PBS), fixed with 4% paraformaldehyde, and then permeabilized with 0.1% Triton X-100.…”

Discovery of lahS as a Global Regulator of Environmental Adaptation and Virulence in Aeromonas hydrophila

“…The E. coli inhibition assay was performed as previously described with some modifications [ 48 ]. A. hydrophila and E. coli BL21 strains grown to an OD 600 of 1.0 and then were concentrated 10 times.…”

Deletion of Polyamine Transport Protein PotD Exacerbates Virulence in Glaesserella (Haemophilus) parasuis in the Form of Non-biofilm-generated Bacteria in a Murine Acute Infection Model

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