Actinomycete Spores


Among bacteria, actinomycetes are a morphologically distinct group that forms multinucleated filaments instead of single cellular units. Within this quantitatively small realm however, the organisms are characterized by a wide range of morphological patterns of development, the variety of dispersal propagules (spores or conidia) produced and their genesis.

Keywords: aleuriospore; aplanospore; arthrospore; bagassosis; endospore; farmer's lung; humidifier fever; mushroom‐worker's lung; germination; maturation; planospore; resistance; taxonomy

Figure 1.

Morphological features of spores. General shape of spores: (a) globose; (b) ovoid; (c) doliform; (d) rod‐shaped; (e) allantoid; (f) reniform. Type of flagellation: (g) monopolar monotrichous; (h) peritrichous; (i) polytrichous; (j) monopolar polytrichous (lophotrichous); (k) subpolar polytrichous; (l) lateral polytrichous. Surface ornamentation: (m) smooth; (n) irregular rugose; (o) parallel rugose; (p) warty; (q) tuberculate; (r) verrucose; (s) spiny; (t) hairy. (Produced by G.Vobis).

Figure 2.

Microtetraspora glauca. Produced by S. Miyadoh and S. Amano.

Figure 3.

Micromonospora olivasterospora. Produced by Y. Gyobu.

Figure 4.

Thermoactinomyces: lysis of hyphae and spore liberation (1, 2); young and mature endospores (3–6). Produced by R. Locci.

Figure 5.

Thermomonospora mesouviformis. The aerial mycelium bears dichotomously branched sporophores on which single heat‐sensitive spores are produced in clusters. Produced by M. Hayakawa, H. Ilno and H. Nomura.

Figure 6.

Actinomadura yumaensis. Produced by S. Miyadoh and S. Amano.

Figure 7.

Microbispora rosea subsp. rosea. Spores in characteristic longitudinal pairs are formed on short sporophores borne on the entire aerial mycelium. Produced by M. Hayakawa, H. Iino and H. Nonomura.

Figure 8.

Spore production within sporangia. Sporangia developed on substrate mycelium: (a) Actinoplanes (including Ampullariella): polysporous (1) globose, (2) cylindrical, (3) lobate, (4) subglobose, (5) irregular; (b) Pilimelia: (6) ovoid, (7) campanulate, (8) cylindrical; (c) Dactylosporangium: oligosporus, claviform. Sporangia developed on aerial mycelium: (d) Planomonospora: monosporous, clavate; (e) Planobispora: disporous, cylindrical; (f) Planotetraspora: tetrasporous, cylindrical; (g) Planopolyspora: polysporous, tubular; (h) Spirillospora: polysporous, globose; (i) Streptosporangium: polysporous, spherical. Produced by G. Vobis.

Figure 9.

Sporangial development in Streptosporangium. (a) The sheath (sd) at the tip of an aerial hypha (hy) expands terminally into a small vesicle. (b) The vesicle is filled out by a single, nonramified, coiled sporogenous hypha (sh), which is separated by a crosswall (se) from the sporangiosphore (sp), forming the sporangial primordium (pr). (c) The sporogenous hypha extends by apical growth and becomes divided into spore‐size compartments; the sheath (sd) of the sporangiophore is continuous with the sporangial envelope (sl). (d) The mature sporangium (sg) is spherical and contains a single coiled chain of nonmotile spores (so). Produced by G. Vobis.

Figure 10.

Actinoplanes regularis characterized by sporangia containing parallel rows of rod‐shaped spores. Produced by G. Vobis.

Figure 11.

Sporangial development in Pilimelia terevasa. (a) A thick hypha (hy), covered by a sheath (sd), protrudes the surface of the substrate. (b) The sporangial primordium (pr) starts with subterminal outgrowths at the tip of the future sporangiophore (sp). (c) The newly formed sporogenous hyphae (sh) branch out and extend apically. (d) The sporogenous hyphae form septa (se) acropetally, the sporangial envelope (sl) swells. (e) In the mature sporangium (sg), the sporogenous hyphae, oriented in parallel, are divided in rod‐shaped spores (so). Produced by G. Vobis.

Figure 12.

Genus Planobispora. A fan‐shaped tuft of six two‐spored sporangia, developed by a single sporangiophore, with the primordium of the seventh sporangium at its apex. Produced by G. Vobis.

Figure 13.

Planomonospora parontospora. Aerial mycelium bearing sporangiophores with numerous sporangia. Produced by G. Vobis.

Figure 14.

Sporangial ontogeny in Spirillospora. (a) An aerial hypha (hy), covered by a sheath (sd), coils at the tip. (b) The coiled hypha starts immediately to ramify (arrowhead) forming sporogenous hyphae (sh), which are enclosed in a common sheath (sd). (c, c′) The sporogenous hyphae (sh) of the sporangial primordium (pr) continue with apical growth and ramification, always held together by the sheath‐like envelope (sl). (d) A laterally inserted sporangiophore (sp) supports the spherical sporangium (sg); the sporogenous hyphae (sh) are divided in spores (so). Produced by G. Vobis.



Cross T (1968) The diversity of bacterial spores. Journal of Applied Bacteriology 33: 95–102.

Holt JH, Krieg NR, Sneath PHA, Staley JT and Williams ST (1994) Bergey's Manual of Determinative Bacteriology, 9th edn. Baltimore: Williams & Wilkins.

Hoskisson PA, Hobbs G and Sharples GP (2000) Response of Micromonospora echinospora (NCIMB 12744) spores to heat treatment with evidence of a heat activation phenomenon. Letters in Applied Microbiology 30: 114–117.

Lacey J (1981) Airborne actinomycete spores as respiratory allergens. Zentralblatt für Bakteriologie, Mikrobiologie und Hygiene I (Supplement 11): 243–250.

Locci R (1988) Comparative morphology of actinomycetes in natural and artificial habitats. In: Okami Y, Beppu T and Ogawara H (eds) Biology of Actinomycetes ’88, pp. 482–489. Tokyo: Japan Scientific Society Press.

Locci R, Baldacci E and Petrolini B (1971) On the spore formation process in actinomycetes. Rivista di Patologia Vegetale (7 Suppl.): 3–80.

Locci R and Sharples G (1984) Morphology. In: Goodfellow M, Mordarski M and Williams ST (eds) The Biology of Actinomycetes, pp. 165–199. London: Academic Press.

Vobis G (1991) The genus Actinoplanes and related genera. In: Balows A, Trumper HG, Dworkin M, Harder W and Schleifer KH (eds) The Prokaryotes, pp. 1029–1060. New York: Springer Verlag.

Vobis G (1997) Morphology of actinomycetes. In: Miyadoh S (ed.) Atlas of Actinomycetes, pp. 180–191. Tokyo: Society for Actinomycetes Japan.

Further Reading

Al‐Diwany LJ and Cross T (1981) Ecological studies on nocardioforms and other actinomycetes in aquatic habitats. Zentralblatt für Bakteriologie, Mikrobiologie und Hygiene I. (Suppl. 11): 153–160.

Attwell RW and Cross T (1973) Germination of actinomycete spores. In: Sykes G and Skinner FA (eds) Actinomycetales. Characteristics and Practical Importance, pp. 197–207. London: Academic Press.

Cross T (1968) Thermophilic actinomycetes. Journal of Applied Bacteriology 31: 36–53.

Cross T (1981) Aquatic actinomycetes: a critical survey of the occurrence, growth and role of actinomycetes in aquatic habitats. Journal of Applied Bacteriology 50: 397–423.

Cross T and Attwell RW (1973) Recovery of viable thermoactinomycete endospores from deep mud cores. In: Barker AN, Gould GW and Wolf J (eds) Spore Research 1972, pp. 11–20. London: Academic Press.

Cross T, Davies FL and Walker PD (1972) Thermoactinomyces vulgaris. I. Fine structure of the developing endospore. In: Barker AN, Gould GW and Wolf J (eds) Spore Research 1971, pp. 175–180. London: Academic Press.

Cross T and Johnston DW (1972) Thermoactinomyces vulgaris. II. Distribution in natural habitats. In: Barker AN, Gould GW and Wolf J (eds) Spore Research 1971, pp. 315–330. London: Academic Press.

Dworkin M (ed.) (1999–2004) The Prokaryotes. An Evolving Electronic Resource for the Microbiological Community (http://link.springer‐ New York: Springer.

Mainelis G, Adhikari A, Willike K et al. (2002) Collection of airborne microorganisms by a new electrostatic precipitator. Journal of Aerosol Science 33: 1417–1432.

Reponen TA, Grinshpun SA, Conwell KL, Wiest J and Anderson M (2001) Aerodynamic versus physical size of spores: measurement and implication for respiratory deposition. Grana 40: 119–125.

Williams ST, Lanning S and Wellington EMH (1984) Ecology of actinomycetes. In: Goodfellow M, Mordarski M and Williams ST (eds) The Biology of Actinomycetes, pp. 481–528. London: Academic Press.

Williams ST, Sharpe ME and Holt JG (eds) (1989) Bergey's Manual of Systematic Bacteriology, vol. 4. Baltimore: Williams & Wilkins.

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Locci, Romano(Jan 2006) Actinomycete Spores. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0004237]