The role of stress in colicin regulation

Abstract

Bacteriocins produced by Enterobacteriaceae are high molecular weight toxic proteins that kill target cells through a variety of mechanisms, including pore formation and nucleic acid degradation. What is remarkable about these toxins is that their expression results in death to the producing cells and therefore bacteriocin induction have to be tightly regulated, often confined to times of stress. Information on the regulation of bacteriocins produced by enteric bacteria is sketchy as their expression has only been elucidated in a handful of bacteria. Here, we review the known regulatory mechanisms of enteric bacteriocins and explore the expression of 12 of them in response to various triggers: DNA-damaging agents, stringent response, catabolite repression, oxidative stress, growth phase, osmolarity, cold shock, nutrient deprivation, anaerobiosis and pH stress. Our results indicate that the expression of bacteriocins is mostly confined to mutagenic triggers, while all other triggers tested are limited inducers.

Making the Best of Aggression: The Many Dimensions of Bacterial Toxin Regulation

“…The expression of most known antibacterial toxin types is tightly regulated [15][16][17][18][19][20], consistent with the fact that the overall costs of toxin production are expected to be significant. Release of many diffusible toxins, like colicins or pyocins, occurs through lysis and death of the producing cells [17,21,22].…”

The Evolution of Mass Cell Suicide in Bacterial Warfare

“…When a colicin producing strain is growing alone, the colicin operon is typically only expressed in a small fraction of the population [9–15]. Expression can be upregulated by DNA damage as the colicin operon is regulated by the SOS response pathway [14,16,17], which is often done artificially via the addition of DNA-damaging agents such as mitomycin C [12,14,16,18,19]. However, many natural colicins also damage DNA, and these too have been shown to upregulate colicin production in targeted cells [9,20], an example of competition sensing [21] (Figure 1).…”

The Role of Background Bacteria in Preventing the Isolation and Detection of Shigella and STEC in Foods and Novel MuSIC ddPCR Method to Improve STEC Detection in the Presence of Background Bacteria

“…In a culture, about 0.1% of the cells produce colicin and cause lysis under normal conditions and this is increased to 3% during nutrient starvation and 50% after SOS response (Bayramoglu et al, 2017). The immunity gene is continuously being expressed at small levels so that a bacterium closely related to the cell releasing colicin can be protected (Ghazaryan et al, 2014). Colicin receptors on bacterial cell membranes are usually receptors that uptake nutrients such as iron and vitamin B12 (Ghazaryan et al, 2014;Kim et al, 2014).…”

“…The immunity gene is continuously being expressed at small levels so that a bacterium closely related to the cell releasing colicin can be protected (Ghazaryan et al, 2014). Colicin receptors on bacterial cell membranes are usually receptors that uptake nutrients such as iron and vitamin B12 (Ghazaryan et al, 2014;Kim et al, 2014). The Tol and Ton transporters translocate the colicin into the cell.…”

“…It is important that the colicin and lysis gene are not induced unnecessarily as the lysis and release of the colicin causes suicide of the cell. Lysing of the cell and colicin release only occurs when the lysis protein has reached a certain concentration threshold(Bayramoglu et al, 2017;Ghazaryan, Tonoyan, Ashhab, Soares, & Gillor, 2014).…”