Publicação
Bacterial communities from an estuarine system: phylogenetic diversity and resistance to a ß-lactms
| Resumo: | Prokaryotic communities are extremely complex and structured entities, composed by extremely abundant and diverse members. Recent advances such as the awareness of the existence of an unculturable prokaryotic majority, and growing progresses on taxonomy based on DNA sequences as well as the establishement of the sequence-based tree of life constituted the support for the development of novel culture-independent molecular techniques that offered new ways of studying microorganisms in diverse environments. In this study culture-independent approaches were applied to characterise the phylogenetic diversity of bacterioplankton communities from Ria de Aveiro. The molecular phylogenetic analysis revealed a prokaryotic diversity comparable to other geographical distinct coastal and estuarine environments previously studied. Compositional shifts within this community occurred essentially between the brackish and freshwater sections. Seasonally driven changes in microbial community in this estuary also occur. The dominant bacterial groups changed from Bacteroidetes, a-Proteobacteria and g-Proteobacteria in the marine-brackish section to Bacteroidetes, b-Proteobacteria, d-Proteobacteria and e-Proteobacteria in the freshwater section of the estuary. Results suggested that salinity and temperature fluctuations accounted for a significant amount of the phylogenetic variability detected along the estuarine gradient. Culture-independent methodologies were also applied to study the diversity of genetic molecular determinants of antibiotic resistance within this estuary, which potentially constitute a risk to human and ecological health. Sequences representing clinical relevant families of b-lactamases were detected in Ria de Aveiro. Most of the retrieved sequences were identical or very similar to b-lactamase gene sequences previously characterised from clinical isolates. Phylogenetic analysis suggests that this aquatic ecosystem is a reservoir of molecular diverse putative bla sequences. Culture-dependent approaches were applied to obtain complementary data on this subject. Considerable levels of prevalence and diversity of b-lactamase genes and integrons were confirmed to occur in Ria de Aveiro. This study reinforces the hypothesis that cultivation-dependent approaches are insufficiently adequate to study the phylogenetic and functional molecular diversities of bacterial communities from natural environments. Taken together obtained results suggested that, whenever possible, complex microbial communities should be studied by using a combination of different cultureindependent methodologies and, when necessary, cultivation-based methods must be applied to the same samples to obtain complementary data. |
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| Autores principais: | Henriques, Isabel da Silva |
| Assunto: | Microbiologia Comunidades microbiológicas Filogenia Antibióticos Bacterioplâncton |
| Ano: | 2006 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Prokaryotic communities are extremely complex and structured entities, composed by extremely abundant and diverse members. Recent advances such as the awareness of the existence of an unculturable prokaryotic majority, and growing progresses on taxonomy based on DNA sequences as well as the establishement of the sequence-based tree of life constituted the support for the development of novel culture-independent molecular techniques that offered new ways of studying microorganisms in diverse environments. In this study culture-independent approaches were applied to characterise the phylogenetic diversity of bacterioplankton communities from Ria de Aveiro. The molecular phylogenetic analysis revealed a prokaryotic diversity comparable to other geographical distinct coastal and estuarine environments previously studied. Compositional shifts within this community occurred essentially between the brackish and freshwater sections. Seasonally driven changes in microbial community in this estuary also occur. The dominant bacterial groups changed from Bacteroidetes, a-Proteobacteria and g-Proteobacteria in the marine-brackish section to Bacteroidetes, b-Proteobacteria, d-Proteobacteria and e-Proteobacteria in the freshwater section of the estuary. Results suggested that salinity and temperature fluctuations accounted for a significant amount of the phylogenetic variability detected along the estuarine gradient. Culture-independent methodologies were also applied to study the diversity of genetic molecular determinants of antibiotic resistance within this estuary, which potentially constitute a risk to human and ecological health. Sequences representing clinical relevant families of b-lactamases were detected in Ria de Aveiro. Most of the retrieved sequences were identical or very similar to b-lactamase gene sequences previously characterised from clinical isolates. Phylogenetic analysis suggests that this aquatic ecosystem is a reservoir of molecular diverse putative bla sequences. Culture-dependent approaches were applied to obtain complementary data on this subject. Considerable levels of prevalence and diversity of b-lactamase genes and integrons were confirmed to occur in Ria de Aveiro. This study reinforces the hypothesis that cultivation-dependent approaches are insufficiently adequate to study the phylogenetic and functional molecular diversities of bacterial communities from natural environments. Taken together obtained results suggested that, whenever possible, complex microbial communities should be studied by using a combination of different cultureindependent methodologies and, when necessary, cultivation-based methods must be applied to the same samples to obtain complementary data. |
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