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Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa
Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collecti...
Autores principales: | , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Frontiers Media S.A.
2019
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558075/ https://www.ncbi.nlm.nih.gov/pubmed/31214140 http://dx.doi.org/10.3389/fmicb.2019.01195 |
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author | Beukes, Chrizelle W. Boshoff, Francois S. Phalane, Francina L. Hassen, Ahmed I. le Roux, Marianne M. Stȩpkowski, Tomasz Venter, Stephanus N. Steenkamp, Emma T. |
author_facet | Beukes, Chrizelle W. Boshoff, Francois S. Phalane, Francina L. Hassen, Ahmed I. le Roux, Marianne M. Stȩpkowski, Tomasz Venter, Stephanus N. Steenkamp, Emma T. |
author_sort | Beukes, Chrizelle W. |
collection | PubMed |
description | Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA-based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria (Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli, M. abyssinicae, M. shonense, and P. tropica. We encountered only a single isolate of Bradyrhizobium, which is in contrast to the dominant association of this genus with Australian Acacia. V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species. |
format | Online Article Text |
id | pubmed-6558075 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | Frontiers Media S.A. |
record_format | MEDLINE/PubMed |
spelling | pubmed-65580752019-06-18 Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa Beukes, Chrizelle W. Boshoff, Francois S. Phalane, Francina L. Hassen, Ahmed I. le Roux, Marianne M. Stȩpkowski, Tomasz Venter, Stephanus N. Steenkamp, Emma T. Front Microbiol Microbiology Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA-based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria (Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli, M. abyssinicae, M. shonense, and P. tropica. We encountered only a single isolate of Bradyrhizobium, which is in contrast to the dominant association of this genus with Australian Acacia. V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species. Frontiers Media S.A. 2019-06-04 /pmc/articles/PMC6558075/ /pubmed/31214140 http://dx.doi.org/10.3389/fmicb.2019.01195 Text en Copyright © 2019 Beukes, Boshoff, Phalane, Hassen, le Roux, Stȩpkowski, Venter and Steenkamp. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. |
spellingShingle | Microbiology Beukes, Chrizelle W. Boshoff, Francois S. Phalane, Francina L. Hassen, Ahmed I. le Roux, Marianne M. Stȩpkowski, Tomasz Venter, Stephanus N. Steenkamp, Emma T. Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title | Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title_full | Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title_fullStr | Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title_full_unstemmed | Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title_short | Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa |
title_sort | both alpha- and beta-rhizobia occupy the root nodules of vachellia karroo in south africa |
topic | Microbiology |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558075/ https://www.ncbi.nlm.nih.gov/pubmed/31214140 http://dx.doi.org/10.3389/fmicb.2019.01195 |
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