by Piter Kehoma Boll
Bacteria are found almost everywhere across our planet and they are essential for the survival of every other lifeform, including the fascinating, and for some disgusting, cockroaches. One special cockroach-friendly genus of bacteria has the adequate name Blattabacterium, whose best-known species is Blattabacterium cuenoti, which I decided to call the “common cockroach bacterium”.
This interesting species, like all species of Blattabacterium, is an obligate endosymbiont of cockroaches, meaning that it can only exists inside cockroach cells. More specifically, the common cockroach bacterium lives inside the cells of the fat bodies of cockroaches, i.e., their adipose tissue. It was found living inside all cockroach species examined to date with the exception of the genus Nocticola. It is also found inside the termite Mastotermes darwinensis because, if you did not know yet, termites are nothing more than highly specialized cockroaches. Thus, it is thought that this bacterium first “infected” the ancestor of all modern cockroaches about 140 million years ago and has only been lost in two lineages, the one from Nocticola and the one from termites.
Although many cockroaches are generalist feeders, being able to feed on almost everything, the main diet of all species is decaying plant material, and this is a relatively nitrogen-poor food. In order to increase their nitrogen intake, cockroaches store uric acid, a common product of protein metabolism. Most animals, including humans, excrete uric acid in their urine, but cockroaches store it in their adipose tissue. Thus, it was originally thought that the cockroach bacteria, by living close to uric acid reserves in the adipose tissue, could use uric acid directly as a food source, but studies have found this is not the case.
When necessary, cockroaches release this uric acid and it is broken down into urea or ammonia by bacteria living in their guts. After that, the common cockroach bacteria can use those compounds to synthesize glutamate, essential amino acids and vitamins for the cockroach.
Since they cannot use uric acid directly, it is a mystery why the common cockroach bacteria lives so close to the place where this substance is stored. One suggestion is that it was originally able to use uric acid but lost this ability by genome reduction.
The functional gene categories of Blattobacterium are very similar to those of Blochmannia, an endosymbiotic bacterium from carpenter ants, which also feed on plant material. However, Blochmannia is very distantly related to Blattobacterium, suggesting that their similar genomes are the result of convergent evolution caused by similar lifestyles.
When something works, nature invents it more than once.
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More on Bacteria:
Friday Fellow: Taq (on 22 January 2016)
Friday Fellow: Witch’s Jelly (on 14 October 2016)
Friday Fellow: Conan the Bacterium (on 6 January 2017)
Friday Fellow: H. pylori (on 8 September 2017)
Friday Fellow: Hay Bacillus (on 14 December 2017)
Friday Fellow: Alder Root Bacterium (on 16 March 2018)
Friday Fellow: Bt (on 1 February 2019)
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López-Sanchez MJ, Neef A, Peretó J, Patiño-Navarrete R, Pignatelli M, Latorre A, Moya A (2009) Evolutionary Convergence and Nitrogen Metabolism in Blattabacterium strain Bge, Primary Endosymbiont of the Cockroach Blattella germanica. PLoS Genetics 5(11): e1000721. 10.1371/journal.pgen.1000721
Patiño-Navarrete R, Moya A, Latorre A, Peretó J (2013) Comparative Genomics of Blattabacterium cuenoti: The Frozen Legacy of an Ancient Endosymbiont Genome. Genome Biology and Evolution 5(2): 351–361. https://doi.org/10.1093/gbe/evt011
Sabree ZL, Kambhapati S, Moran NA (2009) Nitrogen recycling and nutritional provisioning by Blattabacterium, the cockroach endosymbiont. PNAS 106(46): 19521–19256. https://doi.org/10.1073/pnas.0907504106