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Previous issue date: 2017-06-09 / - / Bacteria are important components of the food web structure in aquatic ecosystems
in which they influence the flow of carbon and energy. Populations of bacteria in
these ecosystems comprise a diverse spectrum of individual cells able to respond to
many factors such as nutrient supply, temperature and virus infection, which regulate
bacterial life and death. Bacterial death is a key cellular event involved in the control
and production of bacteria in aquatic ecosystems with functional meaning in the
carbon and nutrient cycles. Therefore, the study of bacterial structural features and
cellular mechanisms underlying bacterial death is crucial to understand processes
affecting the entire population. However, both bacterial structure and cellular events
of death in aquatic ecosystems are still poorly understood. In the present work, we
used single cell approaches to study the structural organization of bacteria as well as
to characterize cellular processes of death in these organisms. First, by using
fluorescence and transmission electron microscopy (TEM), we provided a general
panorama of how microscopy techniques, especially TEM, are powerful tools to
understand bacterial structure and their responses to environmental stresses. We
showed that bacteria from aquatic ecosystems have remarkable ultrastrutural
diversity with components such as bacterial envelope of individual cells differing in
structure within the same population. Second, we sought to identify and characterize
mechanisms of bacterial cell death. Because our TEM analyses revealed
morphological signs of apoptosis, a type of program cell death (PCD), in aquatic
bacteria directly collected from natural ecosystems, we applied different techniques
to detect apoptosis in bacteria cultured from natural samples. We used TEM as well
as different probes to detect this type of PCD in cultured bacteria exposed to
increased temperature and viral infection, which are recognized inducers of bacterial
death. TEM showed, in both situations, ultrastructural changes indicative of
apoptosis, such as cell retraction and condensation, similar to those reported for
eukaryotic cells. Assays for membrane permeability, DNA fragmentation,
phosphatidilserine exposition and caspase activation were significantly increased in
treated bacteria compared to the control group. Altogether, our data demonstrate, for
the first time, that PCD occur in aquatic bacteria, and that this event may be a basic
mechanism for regulation of bacterial communities in these ecosystems.
| Identifer | oai:union.ndltd.org:IBICT/oai:hermes.cpd.ufjf.br:ufjf/6145 |
| Date | 09 June 2017 |
| Creators | Silva, Thiago Pereira da |
| Contributors | Melo, Rossana Correa Netto de, Amado, André Megali, Cardoso, Simone Jaqueline, Farjalla, Vinicius Fortes, Chiarini-Garcia, Helio |
| Publisher | Universidade Federal de Juiz de Fora (UFJF), Programa de Pós-graduação em Ecologia, UFJF, Brasil, ICB – Instituto de Ciências Biológicas |
| Source Sets | IBICT Brazilian ETDs |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFJF, instname:Universidade Federal de Juiz de Fora, instacron:UFJF |
| Rights | info:eu-repo/semantics/embargoedAccess |
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