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Structure and function of the adhesive type IV pilus of Sulfolobus acidocaldarius
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
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2012 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 14, no 12, 3188-3202 p.Article in journal (Refereed) Published
Abstract [en]

Archaea display a variety of type IV pili on their surface and employ them in different physiological functions. In the crenarchaeon Sulfolobus acidocaldarius the most abundant surface structure is the aap pilus (archaeal adhesive pilus). The construction of in frame deletions of the aap genes revealed that all the five genes (aapA, aapX, aapE, aapF, aapB) are indispensible for assembly of the pilus and an impact on surface motility and biofilm formation was observed. Our analyses revealed that there exists a regulatory cross-talk between the expression of aap genes and archaella (formerly archaeal flagella) genes during different growth phases. The structure of the aap pilus is entirely different from the known bacterial type IV pili as well as other archaeal type IV pili. An aap pilus displayed 3 stranded helices where there is a rotation per subunit of ∼ 138° and a rise per subunit of ∼ 5.7 Å. The filaments have a diameter of ∼ 110 Å and the resolution was judged to be ∼ 9 Å. We concluded that small changes in sequence might be amplified by large changes in higher-order packing. Our finding of an extraordinary stability of aap pili possibly represents an adaptation to harsh environments that S. acidocaldarius encounters.

Place, publisher, year, edition, pages
2012. Vol. 14, no 12, 3188-3202 p.
National Category
URN: urn:nbn:se:uu:diva-192617DOI: 10.1111/j.1462-2920.2012.02898.xOAI: oai:DiVA.org:uu-192617DiVA: diva2:600235
Available from: 2013-01-23 Created: 2013-01-23 Last updated: 2015-11-10Bibliographically approved
In thesis
1. Microbial adaptations and controlling mechanisms of surface-associated microhabitat heterogeneity in aquatic systems
Open this publication in new window or tab >>Microbial adaptations and controlling mechanisms of surface-associated microhabitat heterogeneity in aquatic systems
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Habitat heterogeneity is a driving factor for speciation and ecosystem functioning and is well studied in macro-ecology. Yet our understanding of microbial adaptations, and governing processes is incomplete. The here presented thesis aims at giving us a better understanding of patterns in micro-heterogeneity, and microbial adaptations to such heterogeneity with particular focus on surface-dominated, aquatic habitats. The most prominent microbial adaptation to surface associated mode of life is biofilm formation. Biofilms rely heavily on type IV pili. These pili systems are well studied in Bacteria, but largely unknown in Archaea. Therefore, the first part of this thesis focuses on resolving genetic and structural feature of the type IV like aap-pilus of the thermo-acidophilic Sulfolobus acidocaldarius. We found the aap-pilus to be indispensible for biofilm formation, and to be unparalleled in variability of its quaternary structure and cross regulation with other filaments. The second part of this thesis investigates particle colonization in the water column, focusing on diatoms as a model system, allowing an in situ assessment of different stages of particle colonization, and potential particle-specificity of the associated bacterial community. Opposing reports from marine systems, we did not observe diatom-specificity in the associated bacterial community. Instead we found bacterial community subsets, one likely originating from sediment resuspension, and the other being controlled by biofilm-forming populations (e.g. Flexibacter), able to attach to newly formed particle surfaces and subsequently facilitate secondary colonization by other bacteria. Finally, the habitat heterogeneity in top-layers of lake sediments were investigated in experimental microcosms. Cell-specific oxygen consumption rates were determined, to assess microbial activity across different scales. Individual activity rates differed strongly across all investigated scales, likely due to spatially heterogeneous distribution of nutrients with differing quality. Vice versa, the influence of microbial activity on micro-habitat-heterogeneity was investigated. We correlated sediment redox-state with bacterial community composition and populations. Our results indicate that habitat heterogeneity is generally beneficial for microorganism, and greater heterogeneity results in greater bacterial diversity. However, this heterogeneity-diversity relationship is limited and microorganisms actively stabilize their immediate redox environment to a preferred, community-specific, stable state, if cell abundances exceed a minimum threshold.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 69 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1296
microbial habitat heterogeneity
National Category
Biological Sciences
Research subject
Biology with specialization in Limnology
urn:nbn:se:uu:diva-263206 (URN)978-91-554-9351-6 (ISBN)
Public defence
2015-11-20, Ekman Salen, Norbyvägen 14, Uppsala, 13:15 (English)
Available from: 2015-10-27 Created: 2015-09-28 Last updated: 2015-11-10

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