''Mycobacterium ulcerans'' is a species of bacteria found in various aquatic environments. The bacteria can infect humans and some other animals, causing persistent open wounds called

Buruli ulcer Buruli ulcer () is an infectious disease characterized by the development of painless open wounds. The disease is limited to certain areas of the world, most cases occurring in Sub-Saharan Africa and Australia. The first sign of infection is a s ...

. ''M. ulcerans'' is closely related to ''

Mycobacterium marinum ''Mycobacterium marinum'' is a slow growing mycobacterium (SGM) belonging to the genus ''Mycobacterium'' and the phylum Actinobacteria. The strain marinum was first identified by Aronson in 1926 and it is observed as a pathogenic mycobacterium. F ...

'', from which it evolved around one million years ago, and more distantly to the

mycobacteria ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...

which cause

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

and

leprosy Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria ''Mycobacterium leprae'' or ''Mycobacterium lepromatosis''. Infection can lead to damage of the nerves, respiratory tract, skin, and eyes. This nerve damag ...

Description

''M. ulcerans'' are

rod-shaped A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name ''Bacillu ...

bacteria. They appear purple ("

Gram positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...

") under

Gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ...

and bright red ("acid fast") under

Ziehl–Neelsen stain Ziehl–Neelsen staining is a type of acid-fast stain, first introduced by Paul Ehrlich. Ziehl–Neelsen staining is a bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. It is named for two German doctors who modif ...

. On laboratory

media Media may refer to: Communication * Media (communication), tools used to deliver information or data ** Advertising media, various media, content, buying and placement for advertising ** Broadcast media, communications delivered over mass el ...

, ''M. ulcerans'' grow slowly, forming small transparent

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

after four weeks. As colonies age, they develop irregular outlines and a rough, yellow surface.

Taxonomy and evolution

''M. ulcerans'' is a species of

within the phylum

Actinomycetota The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soi ...

. Within the genus ''Mycobacterium'', ''M. ulcerans'' is classified as both a "non-tuberculous mycobacterium" and a "slow-growing mycobacterium". ''M. ulcerans'' likely evolved from the closely related aquatic pathogen ''

'' around one million years ago. The two species are genetically very similar, and have identical

16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRNA ...

genes. However relative to ''M. marinum'', ''M. ulcerans'' has undergone substantial

genome reduction Genome size is the total amount of DNA contained within one copy of a single complete genome. It is typically measured in terms of mass in picograms (trillionths (10−12) of a gram, abbreviated pg) or less frequently in daltons, or as the total ...

, shedding over a thousand

kilobase A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s of genetic content including nearly 1300 genes (23% of the total ''M. marinum'' genes) and sustaining the inactivation of an additional 700 genes. Some of these genes were inactivated by the proliferation of two

mobile genetic elements Mobile genetic elements (MGEs) sometimes called selfish genetic elements are a type of genetic material that can move around within a genome, or that can be transferred from one species or replicon to another. MGEs are found in all organisms. In h ...

, called "IS2404" (213 copies) and "IS2606" (91 copies), neither of which are present in ''M. marinum''. Additionally, ''M. ulcerans'' has acquired a 174 kilobase

plasmid A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...

, termed "pMUM001", which is involved in the production of the toxin

mycolactone Mycolactone is a polyketide-derived macrolide produced and secreted by a group of very closely related pathogenic Mycobacteria species that have been assigned a variety of names including, ''Mycobacterium_ulcerans, M. ulcerans'', ''M. liflandii'' ...

. Other closely related mycobacteria produce mycolactone and infect various aquatic animals; these are sometimes described as distinct species (''M. pseudoshottsii'', ''M. liflandii'', ''M. shinshuense'' and sometimes ''M. marinum'') and sometimes as different lineages of ''M. ulcerans''. Regardless, all mycolactone-producing mycobacteria share a common ancestor distinct from non-mycolactone-producing ''M. marinum''.

Description

Taxonomy and evolution

References

Works cited

External links