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  4. Discovery, Characterization and Ecological Impact of a Predatory Bacterium of Cyanobacteria Responsible for Epidemics in Biocrusts
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Discovery, Characterization and Ecological Impact of a Predatory Bacterium of Cyanobacteria Responsible for Epidemics in Biocrusts

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Description

Predatory bacteria are a guild of heterotrophs that feed directly on other living bacteria. They belong to several bacterial lineages that evolved this mode of life independently and occur in many microbiomes and environments. Current knowledge of predatory bacteria is based on culture studies and simple detection in natural systems. The ecological consequences of their activity, unlike those of other populational loss factors like viral infection or grazing by protists, are yet to be assessed. During large-scale cultivation of biological soil crusts intended for arid soil rehabilitation, episodes of catastrophic failure were observed in cyanobacterial growth that could be ascribed to the action of an unknown predatory bacterium using bioassays. This predatory bacterium was also present in natural biocrust communities, where it formed clearings (plaques) up to 9 cm in diameter that were visible to the naked eye. Enrichment cultivation and purification by cell-sorting were used to obtain co-cultures of the predator with its cyanobacterial prey, as well as to identify and characterize it genomically, physiologically and ultrastructurally. A Bacteroidetes bacterium, unrelated to any known isolate at the family level, it is endobiotic, non-motile, obligately predatory, displays a complex life cycle and very unusual ultrastructure. Extracellular propagules are small (0.8-1.0 µm) Gram-negative cocci with internal two-membrane-bound compartmentalization. These gain entry to the prey likely using a suite of hydrolytic enzymes, localizing to the cyanobacterial cytoplasm, where growth begins into non-compartmentalized pseudofilaments that undergo secretion of vesicles and simultaneous multiple division to yield new propagules. I formally describe it as Candidatus Cyanoraptor togatus, hereafter Cyanoraptor. Its prey range is restricted to biocrust-forming, filamentous, non-heterocystous, gliding, bundle-making cyanobacteria. Molecular meta-analyses showed its worldwide distribution in biocrusts. Biogeochemical analyses of Cyanoraptor plaques revealed that it causes a complete loss of primary productivity, and significant decreases in other biocrusts properties such as water-retention and dust-trapping capacity. Extensive field surveys in the US Southwest revealed its ubiquity and its dispersal-limited, aggregated spatial distribution and incidence. Overall, its activity reduces biocrust productivity by 10% at the ecosystem scale. My research points to predatory bacteria as a significant, but overlooked, ecological force in shaping soil microbiomes.

Date Created
2022
Contributors
  • Bethany Rakes, Julie Ann (Author)
  • Garcia-Pichel, Ferran (Thesis advisor)
  • Gile, Gillian (Committee member)
  • Cao, Huansheng (Committee member)
  • Jacobs, Bertram (Committee member)
  • Arizona State University (Publisher)
Topical Subject
  • Environmental Studies
  • Microbiology
  • Biology
  • biocrust
  • Biological soil crust
  • Cyanobacteria
  • disease agent
  • Predatory Bacteria
  • Restoration
Resource Type
Text
Genre
Doctoral Dissertation
Academic theses
Extent
224 pages
Language
eng
Copyright Statement
In Copyright
Reuse Permissions
All Rights Reserved
Primary Member of
ASU Electronic Theses and Dissertations
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.2.N.168533
Level of coding
minimal
Cataloging Standards
asu1
Note
Partial requirement for: Ph.D., Arizona State University, 2022
Field of study: Natural Science
System Created
  • 2022-08-22 04:28:38
System Modified
  • 2022-08-22 04:29:04
  •     
  • 9 months ago
Additional Formats
  • OAI Dublin Core
  • MODS XML

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