Volutin granules are an
intracytoplasmic storage form of complexed
inorganic
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
polyphosphate
Polyphosphates are salts or esters of polymeric oxyanions formed from tetrahedral PO4 (phosphate) structural units linked together by sharing oxygen atoms. Polyphosphates can adopt linear or a cyclic ring structures. In biology, the polyphosphate e ...
, the production of which is used as one of the identifying criteria when attempting to isolate ''
Corynebacterium diphtheriae'' on
Löffler's medium Löffler's medium is a special substance used to grow diphtheria bacilli to confirm the diagnosis.
History
In 1887, Friedrich Loeffler devised a culture medium containing horse serum, meat infusion, and dextrose for use in the cultivation of co ...
. Polyphosphate granules display the
metachromatic Metachromasia (var. metachromasy) is a characteristical change in the color of staining carried out in biological tissues, exhibited by certain dyes when they bind to particular substances present in these tissues, called chromotropes. For example ...
effect, appearing red when
stained with
methylene blue. Volutin granules can also be found in the cytoplasm of ''
Saccharomyces
''Saccharomyces'' is a genus of fungi that includes many species of yeasts. ''Saccharomyces'' is from Greek σάκχαρον (sugar) and μύκης (fungus) and means ''sugar fungus''. Many members of this genus are considered very important in f ...
'', a genus of
ascomycete 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 ...
.
[Willey, J. M., Sherwood, L. M. and Woolverton, C. J. (2011). Prescott's Microbiology, 8th Ed. McGraw Hill] They are characteristic for different species and depend on the age and condition of the culture.
Volutin granules (metachromatic or Babes-Ernst granules) are highly refractive, strongly basophilic bodies consisting of polymetaphosphate. They appear reddish when stained with polychrome methylene blue or toluidine blue (metachromasia). Special staining techniques such as Albert's or Neisser's demonstrate the granules more clearly. Volutin granules are characteristically present in diphtheria bacilli. Their function is uncertain. They have been considered to represent a reserve of energy and phosphate for cell metabolism but they are most frequent in cells grown under conditions of nutritional deficiency and tend to disappear when the deficient nutrients are supplied.
References
Cell anatomy
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