Growth, luminescence, respiration, and the ATP pool during autoinduction in Beneckea harveyi

Quorum sensing in Chromobacterium violaceum: DNA recognition and gene regulation by the CviR receptor

The bacterial pathogen Chromobacterium violaceum uses a LuxIR-type quorum-sensing system to detect and respond to changes in cell population density. CviI synthesizes the autoinducer C(10)-homoserine lactone (C(10)-HSL), and CviR is a cytoplasmic DNA binding transcription factor that activates gene expression following binding to C(10)-HSL. A number of behaviors are controlled by quorum sensing in C. violaceum. However, few genes have been shown to be directly controlled by CviR, in part because the DNA motif bound by CviR is not well characterized. Here, we define the DNA sequence required for promoter recognition by CviR. Using in vivo data generated from a library of point mutations in a CviR-regulated promoter, we find that CviR binds to a palindrome with the ideal sequence CTGNCCNNNNGGNCAG. We constructed a position weight matrix using these in vivo data and scanned the C. violaceum genome to predict CviR binding sites. We measured direct activation of the identified promoters by CviR and found that CviR controls the expression of the promoter for a chitinase, a type VI secretion-related gene, a transcriptional regulator gene, a guanine deaminase gene, and cviI. Indeed, regulation of cviI expression by CviR generates a canonical quorum-sensing positive-feedback loop.

Luciferase-dependent oxygen consumption by bioluminescent vibrios

Oxygen uptake due to luciferase in two luminous Vibrio species was estimated in vivo by utilizing inhibitors having specificities for luciferase (decanol) and cytochromes (cyanide). Cyanide titration of respiration revealed a component of oxygen uptake less sensitive to cyanide which was completely inhibitable by low concentrations of decanol. From this it was estimated that in vivo luciferase is responsible for less than 12% (Vibrio harveyi) or 20% (Vibrio fischeri) of the total respiration. From these data in vivo bioluminescent quantum yields are estimated to be not lower than 1.7 and 2.6%, respectively.

Evidence for tetradecanal as the natural aldehyde in bacterial bioluminescence

Dim aldehyde mutants of the luminous bacterium Beneckea harveyi emit light with exogenously added long-chain aliphatic aldehyde. In one class of these mutants, luminescence is also stimulated by myristic (tetradecanoic) acid. In such mutants the amount of light obtained by the addition of a small (limiting) amount of either tetradecanal or myristic acid may be increased 60-fold by cyanide and other agents that block respiration. This indicates that the fatty acid product of the luminescent reaction is recycled. The effect, like the stimulation by exogenous fatty acid, exhibits specificity for the 14-carbon compound, suggesting that tetradecanal is the natural aldehyde. In those aldehyde mutants that are not stimulated to emit light by fatty acids, and thus presumably lack the recycling system, the chain-length-specific stimulation by cyanide does not occur.