''Actinoplanes italicus'' is distinguished by the cherry-red color of its vegetative mycelium, and by the production of soluble pigments. It is also known to produce sporangia when cultured on starch or skim milk

agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...

. Very few strains have been found and cultured, thus ''A. italicus'' is relatively uncharacterized.

Characteristics

* Optimum growth temperature is 26 °C * Optimum growth medium is oatmeal agar * Respires aerobically * Gram-positive and motile * Pathogenicity and other health effects are unknown

Discovery

''A. italicus'' was discovered and isolated from a soil sample obtained from an orchard at Pontelongo, Italy.

Laboratory studies

During experiments led by Grazia Beretta searching for antibiotic producers from some of the uncommon genera of the

Actinomycetales The Actinomycetales is an order of Actinomycetota. A member of the order is often called an actinomycete. Actinomycetales are generally gram-positive and anaerobic and have mycelia in a filamentous and branching growth pattern. Some actinomycete ...

, ''A. italicus'' did not produce any antibiotic activity against either Gram-positive or Gram-negative bacteria, and differed in its morphological, cultural, and physiological characteristics. Studies were undertaken to determine whether the first strain, A 52212, of ''A. italicus'' represented a new species of '' Actinoplanes.''

Materials and methods

''A. italicus'' was cultivated using various standard media to determine optimum growth conditions. The media were incubated in the dark at 28 °C. Pigment production was determined by exposing the media to daylight and artificial light at night. Stock slant cultures were kept on oatmeal agar. Every 8 to 16 days, the colony characteristics were observed on starch agar Petri dishes. Using ''A Dictionary of Color'' by Maerz and Paul, color was determined and assigned to the varying pigments produced. Carbon sources were investigated. The media containing carbon sources were inoculated with mycelium, washed twice, and suspended in distilled water. Optimal temperatures were determined by incubating slants of oatmeal agar at 15, 20, 28, 40, and 50 °C.

Macroscopic examination

The notable cherry-red vegetative mycelium is produced on most of the media used in the experiment. Other members of ''Actinoplanes'', when grown on the same media, produced a yellow and orange vegetative mycelium.

Microscopic examination

The vegetative mycelium is composed of thin and twisted

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e. The sporangia produced on starch and skim milk agar have wrinkled surfaces and vary in shapes from spherical to oval and piriform. The shape of the sporangia takes on a more regular shape immediately before rupturing. The spores released are highly motile, taking on varying shapes of spherical and oval.

Physiology

In peptone-yeast extract-iron agar, ''A. italicus'' produces H2S. Within a skim milk agar medium, it was able to hydrolyze casein. Other notable physiological characteristics include its ability to liquefy gelatin, produce tyrosinase, and peptonization without coagulation. The optimal temperature ranges between 28 and 37 °C.

Carbon source

''A. italicus'' uses

inositol Inositol, or more precisely ''myo''-inositol, is a carbocyclic sugar that is abundant in the brain and other mammalian tissues; it mediates cell signal transduction in response to a variety of hormones, neurotransmitters, and growth factors and ...

fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...

rhamnose Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose predominantly occurs in nature in its L-form as L-rhamnose (6-deoxy-L-mannose). This is unusual, since most o ...

, mannitol, xylose,

arabinose Arabinose is an aldopentose – a monosaccharide containing five carbon atoms, and including an aldehyde (CHO) functional group. For biosynthetic reasons, most saccharides are almost always more abundant in nature as the "D"-form, or structurally ...

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

, and glucose as carbon sources for growth. It differs from many members of its genus such as ''A. utahensis'' and ''A. missouriensis'', which do not use inositol; from ''A phillipinesis'' and ''A. armeniacus'', which use raffinose; and from ''A. brasiliensis'' and ''A phillipinesis'', which usw cellulose. ''A. italicus'' is also noted to use natural rubber as a sole carbon source.

Soluble pigments

When cultured in different growth media, ''A. italicus'' tends to produce varying soluble pigments based on its carbon source. On some media, such as nutrient agar, calcium-malate agar, and Bennet's agar, ''A. italicus'' does not produce any pigment at all. On oatmeal, starch, and skim milk agar, the characteristic cherry-red pigment is produced. An amber color is produced when the organism is cultured on Hickey and Tresner agar, potato agar, and nitrate broth, whereas glucose asparagine agar and tyrosine agar would result in a pink color. A deep orange yellowish pigment is produced by growth on Czapek glucose agar.

Phylogeny

''A. italicus'' belongs to the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Actinomycetota. It is most closely related to ''Actinoplanes couchii'' with 98.9% similarity using DNA-DNA hybridization.

''Actinoplanes''

'' Actinoplanes'' belongs to the family Actinoplanaceae. Some characteristics of this genus include able to form motile spores, as well as aerial mycelia and spherica. They are useful in that they can produce

ramoplanin Ramoplanin (INN) is a glycolipodepsipeptide antibiotic drug derived from strain ATCC 33076 of ''Actinoplanes''. It is effective against Gram-positive bacteria. Mechanism It exerts its bacteriocidal effect by inhibiting cell wall biosynthesi ...

, teichoplanin, and valienamine, all of which are critical for the pharmaceutical companies. They generally produce a yellow or orange vegetative mycelium and ordinarily do not produce soluble pigments.

References

External links

Type strain of ''Actinoplanes italicus'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q16973955 Micromonosporaceae Bacteria described in 1973