is introduced into the bacterium after an infection. This is called transduction. Bacteria will resist this by degrading foreign DNA and will use a system called CRISPR sequences, which means the retention of lengths of viral DNA in order to confer resistance to the infection in the future. 3) There can also be conjugation, which is the direct cell-to-cell transfer of the genome, usually among those bacteria in the same species. It can less commonly happen between species, often when conferring antibiotic resistance from one species to another. Each of these is referred to as horizontal gene transfer.
BACTERIAL COMMUNICATION There was once a belief that bacteria did not communicate with one another. This has been found to be untrue. In fact, bacteria that engage in bioluminescence or the giving off of light, will communicate and attract large animal species to their location. When bacteria engage in biofilm production, there are inter-cellular communication strategies that allow cells to act in unison toward the same goal. There can be cellular division of labor, doing things that can’t be done by one cell. Biofilms will increase bacterial resistance many-fold greater than single bacterial organisms. A particular molecular signal we’ve already talked about is quorum sensing. This helps determine how many organisms are in a local population so that, if there are enough organisms, the collective will behave in a particular manner that wouldn’t be done if the population of microorganisms was too low. Gene expression can be coordinated and specific pheromones (a type of hormone) can be released between the cells. Bacteria have the capability to form complicated relationships with other organisms. These include the ability to engage in parasitism, mutualism, and commensalism. Commensal bacteria are harmless to their host and just use the host as a means of growth but not harm to the organisms they reside with or in. There can be predatory bacteria that will kill other bacteria. There is, for example, Myxococcus xanthus, an organism that forms groups of cells that digest and kill other bacteria. Other predatory bacteria will have the ability to attach to and digest other
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