Plant Pathogenic Microbial Communication Affected by Elevated Temperature in Pectobacterium carotovorum subsp....

Area of Science:

• Microbiology
• Plant Pathology
• Bacterial Pathogenesis

Background:

• Gram-negative bacteria use Quorum Sensing (QS) to regulate gene expression based on population density.
• Acyl-Homoserine Lactone (HSL) molecules are key QS signals, with N-(3-oxohexanoyl)-L-Homoserine Lactone (OHHL) central to virulence in Pectobacterium carotovorum subsp. carotovorum (Pcc).
• Environmental factors, particularly temperature, can influence QS signal stability and bacterial virulence.

Purpose of the Study:

• To investigate the effect of incubation temperature on OHHL production and virulence factor expression in Pcc.
• To determine the optimal temperature for OHHL synthesis and disease severity.
• To understand the relationship between temperature, OHHL stability, and Pcc pathogenesis.

Main Methods:

• Pcc cultures were incubated at seven different temperatures (24-37°C).
• OHHL concentration was quantified using violacein units.
• Disease Severity Index (DSI) was measured in cross-inoculated tomato fruits.
• OHHL production kinetics and degradation at different temperatures were analyzed.

Main Results:

• Highest OHHL production (804 violacein units) and DSI (79%) were observed at 33°C.
• OHHL concentration peaked during the late log phase and decreased in stationary/death phases.
• At 35°C and 37°C, OHHL was undetectable, correlating with reduced DSI.
• Signal molecule degradation at elevated temperatures explains reduced virulence.

Conclusions:

• Temperature critically modulates QS-mediated virulence in Pcc, with 33°C being optimal.
• Degradation of OHHL at higher temperatures limits Pcc pathogenesis.
• Findings suggest potential for pathogen adaptation to global warming through altered QS stability.