Bacteria are found almost everywhere on earth and are essential for the survival of all other life, including the fascinating and unpleasant cockroaches. One genus of these symbiotic bacteria in cockroaches is Blattabacterium, and its species most famous is cuclati blattabacterium cuenoti. They decided to call it “bacteria common cockroach”.
Like all Bacillus species, this interesting species is an obligate symbiotic bacterium for cockroaches; meaning that it can only exist in cockroach cells. More specifically, the bacteria common to cockroaches live in the cells of fat of the cockroaches, i.e. in their fabric adipose tissue.
It was found to live in all cockroach species examined so far, except in the genus Spodoptera. Bacteria are also found in termites Mastotermes darwinensisbecause if you don’t already know, termites are highly professional cockroaches. Therefore, it is believed that this bacterium first “infected” all the ancestors of modern cockroaches about 140 million years ago; and it was only lost in the two lineages of Spodoptera and termites.
Fusarium cells are shown in red (top) and grey (bottom). The cyan area in the figure represents the nucleus of cockroach cells. Taken from Sabree et al. (2009)

Although many cockroaches are general carnivores and can eat almost anything, the main diet of all species is decomposing plant materials, which is a relatively depleted food in nitrogen. To increase nitrogen intake, cockroaches store uric acid, a common product of protein metabolism. Most animals, including humans, excrete uric acid in urine, but cockroaches store uric acid in adipose tissue. Therefore, it was originally thought that cockroach bacteria living near uric acid in adipose tissue might directly use uric acid as a food source, but the study showed that this was not the case.
Uric acid
When necessary, cockroaches will release this uric acid, and bacteria in the gut will break it down into urea or ammonia. Thereafter, common cockroach bacteria can use these compounds to synthesise glutamic acid, amino acids essential and vitamins from cockroaches. As they cannot use uric acid directly, it is a mystery why the common cockroach bacteria are so close to the storage site of the substance. One suggestion was that they were initially able to use uric acid, but lost this ability due to genome downsizing.
The functional category of Bacillus genes is very similar to the functional category of genes of the endosymbiont wood ant bacterium Black Spot Disease (Blochmannia), which also feeds on plants. However, the relationship between B. burgdorferi and Bacillus is very distant; indicating that their similar genomes are the result of convergent evolution caused by similar lifestyles.
When something works, nature invents it more than once.