''Rhizomucor pusillus'' is a species of ''

Rhizomucor ''Rhizomucor'' is a genus of fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are cla ...

''. It can cause disease in humans. ''R. pusillus'' is a grey mycelium

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

most commonly found in compost piles. Yellow-brown spores grow on a stalk to reproduce more fungal cells.

Biology

''Rhizomucor pusillus'' is a

thermophilic A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...

fungus that lives in hot environments. Its growth optimum is between 50 and 70 degrees Celsius. It is a good producer of

amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...

. It is

homothallic Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; i.e., having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a si ...

and can cause infections in humans and animals. ''R. pusillus'' cells have stolons,

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be uni ...

s, and branched sporangiophores. Because of the high temperatures required for this microorganism, it is difficult to study in laboratory environments. The ability to utilize different carbon sources can be used differentiate this fungus from other species: it is unable to assimilate sucrose,

glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinog ...

, phenylalanine, and B-alanine.

Diversity

There are three species in the genus ''Rhizomucor''. ''R. pusillus'', '' R. miehei'', and ''R.hizomucor variabilis''. ''R. pusillus'' is the only species of genus that is thermophilic. ''R. variabilis'' and ''R. miehei'' are homogenous and homothallic. Colors of the

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cyc ...

and size and shape of diameter vary between the three species. The degree of intraspecies variability is high. ''R. pusillus'' lives in geothermal places that create and produce their own heat, such as piles of compost and garbage or landfills. Thermophiles reproduce both sexually and asexually. Most common reproduction is asexually, through mitosis. Thermophiles reproduce asexually, when a male spore and a female spore come in contact with each other. Different strains of ''R. pusillus'' segregate into two subclusters at very high levels causing different EST and G6D patterns.

Roles in disease

''Rhizomucor pusillis'' can lead to

zygomycosis Zygomycosis is the broadest term to refer to infections caused by ''bread mold fungi'' of the zygomycota phylum. However, because zygomycota has been identified as polyphyletic, and is not included in modern fungal classification systems, the dise ...

in humans. It causes necrosis of infected tissues and pen neural invasion. It is an incredibly rare disease often found in the lungs of patients with a

weakened immune system Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...

and can often lead to a fatal outcome. It occurs in patients with

hematological malignancies Tumors of the hematopoietic and lymphoid tissues (American English) or tumours of the haematopoietic and lymphoid tissues (British English) are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are al ...

and

diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

as well as

leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...

. ''R. pusillis'' can cause infections in non-human animals as well. In animals the fungus is found in the kidneys and can lead to mucormycotic abortion..

References

*http://www.mycology.adelaide.edu.au/Fungal_Descriptions/Zygomycetes/Rhizomucor/Eucker, J., O. Sezer, B. Graf, and K. Possinger. 2001. Mucormycoses.Mycoses. 44:253-260.Ribes, J. A., C. L. Vanover-Sams, and D. J. Baker. 2000. Zygomycetes in human disease. Clin Microbiol Rev. 13:236-301.Bjorkholm, M., G. Runarsson, F. Celsing, M. Kalin, B. Petrini, and P. Engervall. 2001. Liposomal amphotericin B and surgery in the successful treatment of invasive pulmonary mucormycosis in a patient with acute T- lymphoblastic leukemia. Scand J Infec Dis. 33:316-319.J. Clin. Microbiol. November 2004 vol. 42 no. 11 5400–5402; Pathogenic Fungi in Humans and Animals; edited by D.H. Howard Fungi {{zygomycota-stub