Bacterial Survival and Gene Expression Control
Bacterial survival depends on their capacity to control the gene expression that directs their physiological processes. There is always a need for adaptation because the bacterial environment is always changing, including the temperature and pH.
Quorum Sensing: The Ability to Respond as a Unit
The creation, release, and detection of extracellular signaling molecules called autoinducers that cause the bacterial colony to respond as a single unit is referred to as quorum sensing (Dufour et al. 596). Both Gram-negative and Gram-positive bacteria have shown this kind of reactivity, which enables them to create intricate community structures with significant clinical characteristics.
Autoinducers in Gram-Negative Bacteria
For instance, N-acyl homoserine lactones produced by the Luxl and LuxR genes are employed as the autoinducer in Gram-negative bacterial cells. Once this molecule is released, it initiates a cascade that results in the production of extracellular enzymes like hemolysins, elastase that signals all the colony to change their physiological and phenotypic functions (Dufour et al. 596). For instance, Pseudomonas aeruginosa usually responsible for opportunistic infections in immunocompromised individuals can be activated to virulence cycle.
Peptide-Mediated Quorum Sensing in Gram-Positive Bacteria
On the other hand, Gram-positive bacteria use peptide-mediated quorum sensing modes for the development of genetic competence, such as Conjugation in Enterococcus faecalis, and production of antimicrobial peptides by several Gram-positive bacterial species (Hoyland et al. 364). The peptide used by Gram-positive as an autoinducer is secreted by an ATP Binding Cassette exporter (ABC). The secretion of this peptide increases with an increase in cell density and is detected by kinase sensors in the genetic circuit. When the peptide interacts with the sensor, it activates a phosphorylation cascade that induces the regulator to start DNA binding, leading to the alteration of transcription genes involved in the quorum sensing and hence new phenotypic functions (Hoyland et al. 364).
Work Cited
Dufour, Delphine, and Céline M. Lévesque. “Bacterial behaviors associated with the quorum-sensing peptide pheromone (‘alarmone ‘) in streptococci.” Future microbiology 8.5 (2013): 593-605.
Høyland-Kroghsbo, Nina Molin, Rasmus Baadsgaard Mærkedahl, and Sine Lo Svenningsen. “A quorum-sensing-induced bacteriophage defense mechanism.” MBio 4.1 (2013): 362-382.
