Streptomycete Spores

Abstract

Gram‐positive bacteria of the genus Streptomyces are major inhabitants of soil and grow as branching hyphae, strikingly like the filamentous fungi. Whereas their mycelium is multicellular, dispersal and long‐term survival are achieved by unicellular spores. Spore formation is part of a complex developmental cycle involving dedicated reproductive aerial hyphae. The long apical cells of the aerial hyphae are divided into chains of tens of prespore compartments, which in turn mature into thick‐walled spores with condensed nucleoids and low metabolic activity, primed for dispersal and survival. Aerial hyphae and spore surfaces are coated with a proteinaceous fibrous sheath. This highly hydrophobic sheath is required for aerial hyphal emergence, and may aid spore dispersal and interaction with various interfaces. When exposed to appropriate environmental conditions, spores rehydrate and swell. Cell polarisation is required for the emergence of a germ tube, which develops into a mycelium by apical growth and side‐branch formation. Key Concepts: Streptomyces spores are distinctly different from bacterial endospores. Spores develop from dedicated reproductive structures called aerial hyphae. Streptomyces spores are formed by division of long, multigenomic hyphal cells into unigenomic compartments. A thick spore wall is assembled from within the maturing spore and contributes to quiescence and resilience. Spores are dehydrated, accumulate trehalose and have condensed nucleoids. An outer fibrous sheath confers surface hydrophobicity to aerial hyphae and spores. Germination involves rehydration, symmetrical swelling and establishment of polar growth leading to germ tube emergence.

Quality of Irrigation Water Affects Soil Functionality and Bacterial Community Stability in Response to Heat Disturbance

“…Other soil groups, such as members of the Actinobacteria phylum that were abundant in W, FW, and TW controls or Flavobacteriia that were abundant in FW and TW controls, were sensitive to the heat stress. These results suggest that Actinobacteria spores have lower survivorship than the Firmicutes, as previously described for Streptomyces (38). This also shows that they do not have the same growth rate capacities as Proteobacteria as previously proposed by Van der Voort et al (39).…”

A respiratory nitrate reductase active exclusively in resting spores of the obligate aerobe Streptomyces coelicolor A3(2)

“…In contrast to most other bacteria, streptomycetes are multicellular and their life cycle includes three differentiated states: vegetative hyphae develop into multinucleate filaments called aerial hyphae, which develop further into chains of spores (Chater, ). Although Streptomyces spores are relatively resistant to both desiccation and exposure to moderately high temperature they are not nearly as robust as the endospores produced by low‐GC Gram‐positive firmicutes (Hardisson et al ., ; Elliot and Flärdh, ). This has led to the proposal that the main function of streptomycete spores is as a means of rapid dispersal to new environments (Kalakoutskii and Agre, ; Hardisson et al ., ; Elliot and Flärdh, ).…”

“…Although Streptomyces spores are relatively resistant to both desiccation and exposure to moderately high temperature they are not nearly as robust as the endospores produced by low‐GC Gram‐positive firmicutes (Hardisson et al ., ; Elliot and Flärdh, ). This has led to the proposal that the main function of streptomycete spores is as a means of rapid dispersal to new environments (Kalakoutskii and Agre, ; Hardisson et al ., ; Elliot and Flärdh, ). Nevertheless, when they are released from spore chains, the spores can maintain viability for considerable periods of time (Williams et al ., ; Wang et al ., ).…”

Molecular and cytological analysis of the expression ofStreptomycessporulation regulatory genewhiH

“…Long sporogenic apical cells of the aerial hyphae are divided into prespore compartments by a specialized type of cell division that gives rise to multiple and synchronously forming sporulation septa (for recent reviews, see Jakimowicz & van Wezel, 2012;McCormick & Fl€ ardh, 2012). Each prespore receives one copy of the genome and then matures to a spore in a process involving rounding up of the cylindrical compartments, thickening of the cell wall, condensation of DNA, and synthesis of a spore pigment (Elliot & Fl€ ardh, 2012).…”