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. 1988 Dec;54(12):2986–2995. doi: 10.1128/aem.54.12.2986-2995.1988

Floc Formation by Azospirillum lipoferum Grown on Poly-β-Hydroxybutyrate †

Bruce H Bleakley 1, Murray H Gaskins 1, David H Hubbell 1,*, Stephan G Zam 1
PMCID: PMC204416  PMID: 16347792

Abstract

Azospirillum lipoferum RG6xx was grown under conditions similar to those resulting in encystment of Azotobacter spp. A. lipoferum produced cells of uniform shape when grown on nitrogen-free β-hydroxybutyrate agar. Cells accumulated poly-β-hydroxybutyrate and often grew as chains or filaments that eventually lost motility and formed capsules. Within 1 week, vegetative A. lipoferum inocula were converted into microflocs arising from filaments or chains. Cells within microflocs were pleomorphic, contained much poly-β-hydroxybutyrate, and were encapsulated. Some cells had a cystlike morphology. Up to 57% of the dry weight of encapsulated flocs was poly-β-hydroxybutyrate, whereas vegetative cells grown in broth with combined nitrogen had only 3% of their dry weight as poly-β-hydroxybutyrate. Neither encapsulated cells in flocs nor nonencapsulated vegetative cells were significantly desiccation resistant. Under starvation conditions (9 days) only 25% of encapsulated cells remained viable, whereas vegetative cells multiplied severalfold. In short-term germination experiments with encapsulated flocs, nitrate, ammonium, and soil extract promoted formation of motile vegetative cells. Most cells in treatments lacking combined nitrogen eventually depleted their visible poly-β-hydroxybutyrate reserves without germinating. The remaining cells retained the reserve polymer and underwent size reduction.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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