Monitoring of Vibrio harveyi quorum sensing activity in real time during infection of brine shrimp larvae

Abstract

Quorum sensing, bacterial cell-to-cell communication, has been linked to the virulence of pathogenic bacteria. Indeed, in vitro experiments have shown that many bacterial pathogens regulate the expression of virulence genes by this cell-to-cell communication process. Moreover, signal molecules have been detected in samples retrieved from infected hosts and quorum sensing disruption has been reported to result in reduced virulence in different host-pathogen systems. However, data on in vivo quorum sensing activity of pathogens during infection of a host are currently lacking. We previously reported that quorum sensing regulates the virulence of Vibrio harveyi in a standardised model system with gnotobiotic brine shrimp (Artemia franciscana) larvae. Here, we monitored quorum sensing activity in Vibrio harveyi during infection of the shrimp, using bioluminescence as a read-out. We found that wild-type Vibrio harveyi shows a strong increase in quorum sensing activity early during infection. In this respect, the bacteria behave remarkably similar in different larvae, despite the fact that only half of them survive the infection. Interestingly, when expressed per bacterial cell, Vibrio harveyi showed around 200-fold higher maximal quorum sensing-regulated bioluminescence when associated with larvae than in the culture water. Finally, the in vivo quorum sensing activity of mutants defective in the production of one of the three signal molecules is consistent with their virulence, with no detectable in vivo quorum sensing activity in AI-2-and CAI-1-deficient mutants. These results indicate that AI-2 and CAI-1 are the dominant signals during infection of brine shrimp.

Exposure to Static Magnetic Field Stimulates Quorum Sensing Circuit in Luminescent Vibrio Strains of the Harveyi Clade

“…In this regard, it is worthy of note the study of Defoirdt and Sorgeloos [77], which proposed a possible integration of a host cue into the QS circuit. This cue might be represented by the local magnetic field.…”

Inhibition ofSteptococcus mutansbiofilm formation by extracts ofTenacibaculumsp. 20J, a bacterium with wide-spectrum quorum quenching activity

“…The strains used for the AI-2 bioassay, Vibrio harveyi BB170 (HAI-1 negative; AI-2 positive; CAI-1 positive), V. harveyi JMH597 (HAI-1 negative; AI-2 positive; CAI-1 negative) [30], and V. harveyi JAF548, in which bioluminescence is not under the control of QS systems due to the permanent activation of the QS-dependent bioluminescence repressor LuxO [31,32], were cultured in LB supplemented with 30 μg ml −1 of the antibiotic kanamycin (LB+Km) and in autoinducer bioassay medium (AB) [33]. …”

“…V. harveyi BB170 (HAI-1 negative; AI-2 positive; CAI-1 positive), V. harveyi JMH597 (HAI-1 negative; AI-2 positive; CAI-1 negative), and the QS-independent bioluminescent strain V. harveyi JAF548 were used as biosensor strains [30–32]. They were grown overnight in MB at 30°C with shaking.…”

The Apparent Quorum-Sensing Inhibitory Activity of Pyrogallol Is a Side Effect of Peroxide Production

“…We previously showed that the virulence of Vibrio harveyi BB120 (ϭ ATCC BAA-1116; recently reclassified as Vibrio campbellii [6]) in our model system with gnotobiotic brine shrimp larvae is regulated by quorum sensing (7). Using this model system, we investigated whether pyrogallol could protect challenged larvae from the pathogen and found that when added to the culture water at 10 mg · liter Ϫ1 or more, the compound significantly increased the survival of challenged larvae (Table 1).…”