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Special feature "Bugs and Microbugs: bacteria and insects"

Bugs that live in bugs--you may never have thought about it but bacteria live in insects too. In many cases the micro-organisms are absolutely required for the insects to survive, since they provide nutrients and vitamins. In return the insects provide a protected environment in the form of specialized cells in their body. Read about this interesting symbiosis between bacteria and insects (Source: Uni York, UK). This is nothing new. Insects trapped in amber some 30 million years ago already had bacteria in their intestines. What is shocking to many microbiologists is that these bacteria were still alive, as is claimed by the group who isolated them (Source: Whyfiles.org).

Just like any other organism, insects can suffer from bacterial diseases

Here is a weird example of pathogenic bacteria: certain Rickettsia species kill male insects only, but leave the females undisturbed. Such behaviour has serious consequences on the insect population. It is now being investigated to see if these bacteria can be used to combat pest insects (Source: CDC).
Biological warfare against insects using bacteria is not at all science-fiction. Such biological control is common practice, for instance using Bacillus thuringiensis. These bacteria produce a natural insecticide produced by bacteria that kills many types of crop pest insects, but is harmless to humans.

Read more about Bacillus thuringiensis toxin (Bt) (Source: Cornell University). Not all agree to this method Greenpeace about Bt (Source: Greenpeace International).
Why not make the plants produce Bt themselves? Biotechnology made it possible, but Genetically Modified Crops have their own problems (Source: MPR News).
Bacteria can also be used for control of mosquitos, for instance for control of malaria, or other mosquito-borne diseases (Source: Intl. Development Research Centre).
More about biopesticides (source: Access Excellence).

The life cycle of insecticide bacteria can be quite complex. For instance, Photorhabdus luminescens lives inside nematodes (tiny worms) and these worms bury themselves in soil insects where the bacteria are released in the bloodstream of the new host. There the bacteria make the insect glow up and explode, a macabre process but required for the life cycle for these weird bacteria (Source: University of Bath).

Fortunately for the insects, they are not completely helpless against bacterial disease: insects have an immune system too (Source: Entomology course Uni Nebraska).

One of the weirdest discoveries is that bacteria can speed up evolution of insects. The culprit is Wolbachia: a bacterium that lives inside insects and that changes their mating patterns or even their sexes!

Let's turn the fight around: insects killing bacteria. This may be of importance when dealing with bacteria that have become resistant against antibiotics. Not a nice idea, but already known in the Middle-Ages: maggots can heal wounds (for strong stomachs only) (Source: Worsley School Science Pages).

Animals, insects, even plants can suffer from bacterial diseases. And in the latter case, insects can transmit the bacteria. Just like ticks can infect humans with a bacterial infection (for instance Lyme's disease, caused by Borrelia burgdorferi), insects can transfer Xylella fastidiosa to plants, and these bacteria cause severe disease in grapevines, almond, alfalfa and other crop plants (Source: AH Purcell).

Plants, insects (in fact all animals) and bacteria are all part of an ecosystem that can easily be disturbed. Man-made ecosystems require high crops of desired plants, and little growth of weeds. Insects that eat crops instead of weeds are unwanted, and we do our best to change the balance to our favor. It is now recognized that bacteria should not be ignored. Bacteria may be crucial in weed biocontrol by insects (Source: ARS USDA).

Next time you notice an insect maybe you'll think of its bacteria too.

The content of this page is copyright of the Virtual Museum of Bacteria and was written by Dr. T. M. Wassenaar (curator), with support of the Foundation for Bacteriology.
Special Feature files cover various aspects of bacteria, bacteriology, and bacterial diseases and were produced with support from

The Waksman Foundation for Microbiology.

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Page last modified: 08 Mar 2005

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