BACTERIA
MAKE LETHAL PROTEINS TO KILL OTHER ORGANISMS
Before discussing human biological
combat, let’s remember that biological warfare has been practiced throughout
evolutionary history by organisms at all levels on theevolutionary scale. Many
of the following examples have already been discussed under different headings;
here, we will summarize them briefly before talking about deliberate use of
biological agents in human conflict.
When related bacteria compete for the
same habitat or same resources, they often kill each other, using toxic
proteins known as bacteriocins . Generally speaking, bacteria are most likely
to kill their close relatives because the more closely related two strains of
bacteria are, the more likely they will compete for the same resources. For
example, many strains of Escherichia coli deploy a wide variety of
bacteriocins, referred to as colicins , intended to kill other strains of the
same species. The genes for colicins are normally carried on plasmids. The
colicin plasmids of E. coli have been used as the basis of many plasmids
commonly used in molecular biology and genetic engineering . Yersinia pestis
, the plague bacterium, also makes bacteriocins, called pesticins in this
case, designed to kill competing strains of its own species.
When proteins produced by bacteria act
against higher organisms we refer to them as toxins . The difference in
terminology between bacteriocin and toxin is thus really a matter
of perspective. Bacteria deploy bacteriocins against their fellow bacteria with
the deliberate intention of killing them. In contrast, pathogenic bacteria do
not usually “intend” to kill the people they infect. The longer the host
organism stays alive, the longer it provides a home for the infecting bacteria.
Bacteria also infect insects and make toxins that kill insects but are harmless
to vertebrates. The bacterium Bacillus thuringiensishas become famous
for its production of a toxin that kills insect pests.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.