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Micciulla JL, Shor LM, Gage DJ. Enhanced transport of bacteria along root systems by protists can impact plant health. Appl Environ Microbiol 2024; 90:e0201123. [PMID: 38534145 PMCID: PMC11022564 DOI: 10.1128/aem.02011-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 01/25/2024] [Indexed: 03/28/2024] Open
Abstract
Soil protists have been shown to contribute to the structure and function of the rhizosphere in a variety of ways. Protists are key contributors to nutrient cycling through the microbial loop, where biomass is digested by protists and otherwise stored nutrients are returned to the environment. Protists have also been shown to feed on plant pathogenic bacteria and alter root microbiomes in ways that may benefit plants. Recently, a mechanism involving bacterial transport, facilitated by protists, has been hypothesized to contribute to the spatial distribution of bacteria in the rhizosphere. Here, we observe the differential abilities of three soil protists: a ciliate (Colpoda sp.), a flagellate (Cercomonas sp.), and a naked amoeba (Acanthamoeba castellanii) to transport nitrogen-fixing Sinorhizobium meliloti to infectible root tips. Co-inoculation of protists plus S. meliloti resulted in the movement of bacteria, as measured by the presence of nitrogen-fixing nodules, up to 15 cm farther down the root systems when compared to plants inoculated with S. meliloti alone. Co-inoculation of the ciliate, Colpoda sp., with S. meliloti, resulted in shoot weights that were similar to plants that grew in nitrogen-replete potting mix. Colpoda sp.-feeding style and motility likely contributed to their success at transporting bacteria through the rhizosphere. We observed that the addition of protists alone without the co-inoculum of S. meliloti resulted in plants with larger shoot weights than control plants. Follow-up experiments showed that protists plus their associated microbiomes were aiding in plant health, likely through means of nutrient cycling.IMPORTANCEProtists represent a significant portion of the rhizosphere microbiome and have been shown to contribute to plant health, yet they are understudied compared to their bacterial and fungal counterparts. This study elucidates their role in the rhizosphere community and suggests a mechanism by which protists can be used to move bacteria along plant roots. We found that the co-inoculation of protists with nitrogen-fixing beneficial bacteria, Sinorhizobium meliloti, resulted in nodules farther down the roots when compared to plants inoculated with S. meliloti alone, and shoot weights similar to plants that received nitrogen fertilizer. These data illustrate the ability of protists to transport viable bacteria to uninhabited regions of the root system.
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Affiliation(s)
- Jamie L. Micciulla
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado, USA
- Department of Molecular and Cellular Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Leslie M. Shor
- Center for Environmental Sciences & Engineering, University of Connecticut, Storrs, Connecticut, USA
| | - Daniel J. Gage
- Department of Molecular and Cellular Biology, University of Connecticut, Storrs, Connecticut, USA
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Cortés-Pérez S, Ferrera-Cerrato R, Rodríguez-Zaragoza S, Alarcón A. Short-Term Evaluation of the Spatial Distribution of Trophic Groups of Amoebae in the Rhizosphere of Zea mays Inoculated with Rhizophagus intraradices. MICROBIAL ECOLOGY 2022:10.1007/s00248-022-02132-3. [PMID: 36331579 DOI: 10.1007/s00248-022-02132-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
Primary production in terrestrial ecosystems is sustained by plants, microbiota, and fungi, which are the major organic matter providers in the root zone, setting in motion the soil food webs. Predators like soil amoebae voraciously feed on bacteria, fungi, and microbial eukaryotes releasing the nutrients sequestered in their biomass. Early food web setting up is crucial for seedling nutrition and its further development after establishment. Mycorrhizal fungi are more than phosphorus providers, and we wonder what their role is in structuring the predators' trophic groups in the root zone. We evaluated the effect of Rhizophagus intraradices inoculated in Zea mays (mycorrhizosphere), on the structuration of amoebae trophic groups along vertical and horizontal (3, 6, and 9 cm) soil distribution when compared to un-inoculated plants, after 20 days in microcosms. Amoebae species richness was highest in non-mycorrhizal seedlings in the root zone at 6- to 9-cm depth, and 3 cm away from plants. More bacterial species are needed when plants are devoid of mycorrhiza, and their influence is constrained 3 cm away from roots. Higher diversity of trophic groups was recorded at mycorrhizal seedlings and at the compartment influenced by the mycelium at 6- to 9-cm depth. The highest bacterivorous diversity, higher number of rare species and protozoa-eating amoebae, and the absence of fungivorous group recorded at the mycorrhizosphere of Z. mays, indicate that the community was very different from the non-mycorrhizal plants. We conclude that the arbuscular mycorrhizal fungus exerts significant changes on the community of trophic groups of amoebae.
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Affiliation(s)
- Sandra Cortés-Pérez
- Microbiologia de Suelos, Posgrado de Edafología, Colegio de Postgraduados, Carretera Mexico-Texcoco Km. 36.5, Montecillo, 56230, Texcoco, Estado de Mexico, Mexico
| | - Ronald Ferrera-Cerrato
- Microbiologia de Suelos, Posgrado de Edafología, Colegio de Postgraduados, Carretera Mexico-Texcoco Km. 36.5, Montecillo, 56230, Texcoco, Estado de Mexico, Mexico.
| | - Salvador Rodríguez-Zaragoza
- Laboratorio de Ecología Microbiana, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autonoma de Mexico, Av de los Barrios 1, 54090, Los Reyes Iztacala, Estado de Mexico, Mexico
| | - Alejandro Alarcón
- Microbiologia de Suelos, Posgrado de Edafología, Colegio de Postgraduados, Carretera Mexico-Texcoco Km. 36.5, Montecillo, 56230, Texcoco, Estado de Mexico, Mexico
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Abraham JS, Sripoorna S, Dagar J, Jangra S, Kumar A, Yadav K, Singh S, Goyal A, Maurya S, Gambhir G, Toteja R, Gupta R, Singh DK, El-Serehy HA, Al-Misned FA, Al-Farraj SA, Al-Rasheid KA, Maodaa SA, Makhija S. Soil ciliates of the Indian Delhi Region: Their community characteristics with emphasis on their ecological implications as sensitive bio-indicators for soil quality. Saudi J Biol Sci 2019; 26:1305-1313. [PMID: 31516362 PMCID: PMC6733776 DOI: 10.1016/j.sjbs.2019.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/11/2019] [Accepted: 04/15/2019] [Indexed: 11/19/2022] Open
Abstract
The present investigation aims to study the diversity of ciliates from different habitats in and around Delhi, India, and the correlation of this diversity with soil quality {agricultural lands (site 1 and 2), dump yards (site 3 and 4), sewage treatment plant (site 5), residential land (site 6), landfill (site 7) and barren land (site 8)}. Various physicochemical parameters of the different soil samples were studied and analysed for soil texture, interstitial water, pH, conductivity, total organic carbon, total organic matter, total nitrogen and phosphorous content, using standard protocols. Seventeen ciliate taxa belonging to four classes, seven orders, ten families, and 17 genera were recorded, with the maximum number of species (eleven) belonging to the class Spirotrichea. Ciliate diversity was highest at sites 5 and 6 and lowest at sites 1 and 2. Spathidium sp. was the dominant species in the conditioned land (site 8), while the ciliate Colpoda sp. was present in all the sites examined, showing the highest population density in the sewage treatment plant site (site 5). Statistical analysis showed that ciliate diversity was positively correlated to physicochemical parameters such as interstitial water, total organic matter and organic carbon, total nitrogen and total phosphorous content. Analyses of spirotrichs/colpodids (S/C) ratio and diversity indices implied that the habitat conditions of sites 1, 2, 3 and 8 are relatively unfavourable for soil ciliates to flourish; while sites 4, 5, 6 and 7 provided more favourable conditions. The ubiquity of ciliate distribution suggests their important role in the soil food webs and nutrient cycling, and their community structure and specific characteristics appear to be of major importance for soil formation. A full understanding of soil ciliate diversity and physicochemical parameters helps to inform best practice for improving soil quality as well as conservation practices for sustainable development and management of farms and cultivated lands. In conclusion, ciliate diversity serves as an important and sensitive bio-indicator for soil quality.
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Affiliation(s)
- Jeeva Susan Abraham
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - S. Sripoorna
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Jyoti Dagar
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Shiv Jangra
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Anit Kumar
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Khushi Yadav
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Simran Singh
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Anusha Goyal
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Swati Maurya
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Geetu Gambhir
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Ravi Toteja
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
| | - Renu Gupta
- Maitreyi College, University of Delhi, Bapu dham, Chanakyapuri, New Delhi, India
| | | | - Hamed A. El-Serehy
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
- Department of Oceanography, College of Science, Port Said University, Port Said, Egypt
| | - Fahad A. Al-Misned
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Saleh A. Al-Farraj
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Khaled A. Al-Rasheid
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Saleh A. Maodaa
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Seema Makhija
- Acharya Narendra Dev College, University of Delhi, Govindpuri, Kalkaji, New Delhi, India
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Geisen S, Mitchell EAD, Adl S, Bonkowski M, Dunthorn M, Ekelund F, Fernández LD, Jousset A, Krashevska V, Singer D, Spiegel FW, Walochnik J, Lara E. Soil protists: a fertile frontier in soil biology research. FEMS Microbiol Rev 2018; 42:293-323. [DOI: 10.1093/femsre/fuy006] [Citation(s) in RCA: 212] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 02/12/2018] [Indexed: 12/27/2022] Open
Affiliation(s)
- Stefan Geisen
- Department of Terrestrial Ecology, Netherlands Institute of Ecology, 6708 PB Wageningen, The Netherlands
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Edward A D Mitchell
- Laboratory of Soil Biodiversity, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel 2000, Switzerland
- Jardin Botanique de Neuchâtel, Chemin du Perthuis-du-Sault 58, Neuchâtel 2000, Switzerland
| | - Sina Adl
- Department of Soil Sciences, College of Agriculture and Bioresources, University of Saskatchewan, 51 Campus Drive, Saskatoon, Canada
| | - Michael Bonkowski
- Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Institute of Zoology, Terrestrial Ecology, Zülpicher Straße 47b, 50674 Köln, Germany
| | - Micah Dunthorn
- Department of Ecology, University of Kaiserslautern, Erwin-Schrödinger Straße, 67663 Kaiserslautern, Germany
| | - Flemming Ekelund
- Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark
| | - Leonardo D Fernández
- Centro de Investigación en Recursos Naturales y Sustentabilidad (CIRENYS), Universidad Bernardo O’Higgins, Avenida Viel 1497, Santiago, Chile
| | - Alexandre Jousset
- Department of Ecology and Biodiversity, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Valentyna Krashevska
- University of Göttingen, J.F. Blumenbach Institute of Zoology and Anthropology, Untere Karspüle 2, 37073 Göttingen, Germany
| | - David Singer
- Laboratory of Soil Biodiversity, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel 2000, Switzerland
| | - Frederick W Spiegel
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, 72701, United States of America
| | - Julia Walochnik
- Molecular Parasitology, Institute of Tropical Medicine, Medical University, 1090 Vienna, Austria
| | - Enrique Lara
- Laboratory of Soil Biodiversity, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel 2000, Switzerland
- Real Jardín Botánico, CSIC, Plaza de Murillo 2, 28014 Madrid, Spain
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Bobrov AA, Zaitsev AS, Wolters V. Shifts in soil testate amoeba communities associated with forest diversification. MICROBIAL ECOLOGY 2015; 69:884-894. [PMID: 25820471 DOI: 10.1007/s00248-015-0607-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 03/23/2015] [Indexed: 06/04/2023]
Abstract
We studied changes of testate amoeba communities associated with the conversion of spruce monocultures into mixed beech-fir-spruce forests in the Southern Black Forest Mountains (Germany). In this region, forest conversion is characterized by a gradual development of beech undergrowth within thinned spruce tree stands leading to multiple age continuous cover forests with a diversified litter layer. Strong shifts in the abundance of testate amoeba observed in intermediate stages levelled off to monoculture conditions again after the final stage of the conversion process had been reached. The average number of species per conversion stage (i.e., local richness) did not respond strongly to forest conversion, but the total number of species (i.e., regional richness) was considerably higher in the initial stage than in the mixed forests, due to the large number of hygrophilous species inhabiting spruce monocultures. Functional diversity of the testate amoeba community, however, significantly increased during the conversion process. This shift was closely associated with improved C and N availability as well as higher niche diversity in the continuous cover stands. Lower soil acidity in these forests coincided with a higher relative abundance of eurytopic species. Our results suggest that testate amoeba communities are much more affected by physicochemical properties of the soil than directly by litter diversity.
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Affiliation(s)
- Anatoly A Bobrov
- Faculty of Soil Science, Moscow State University, Leninskie Gory, Moscow, 119992, Russia
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6
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Narihiro T, Suzuki A, Yoshimune K, Hori T, Hoshino T, Yumoto I, Yokota A, Kimura N, Kamagata Y. The combination of functional metagenomics and an oil-fed enrichment strategy revealed the phylogenetic diversity of lipolytic bacteria overlooked by the cultivation-based method. Microbes Environ 2014; 29:154-61. [PMID: 24859309 PMCID: PMC4103521 DOI: 10.1264/jsme2.me14002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Metagenomic screening and conventional cultivation have been used to exploit microbial lipolytic enzymes in nature. We used an indigenous forest soil (NS) and oil-fed enriched soil (OS) as microbial and genetic resources. Thirty-four strains (17 each) of lipolytic bacteria were isolated from the NS and OS microcosms. These isolates were classified into the (sub)phyla Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria, all of which are known to be the main microbial resources of commercially available lipolytic enzymes. Seven and 39 lipolytic enzymes were successfully retrieved from the metagenomic libraries of the NS and OS microcosms, respectively. The screening efficiency (a ratio of positive lipolytic clones to the total number of environmental clones) was markedly higher in the OS microcosm than in the NS microcosm. Moreover, metagenomic clones encoding the lipolytic enzymes associated with Alphaproteobacteria, Deltaproteobacteria, Acidobacteria, Armatimonadetes, and Planctomycetes and hitherto-uncultivated microbes were recovered from these libraries. The results of the present study indicate that functional metagenomics can be effectively used to capture as yet undiscovered lipolytic enzymes that have eluded the cultivation-based method, and these combined approaches may be able to provide an overview of lipolytic organisms potentially present in nature.
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Affiliation(s)
- Takashi Narihiro
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
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7
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Gimenez G, Bertelli C, Moliner C, Robert C, Raoult D, Fournier PE, Greub G. Insight into cross-talk between intra-amoebal pathogens. BMC Genomics 2011; 12:542. [PMID: 22047552 PMCID: PMC3220658 DOI: 10.1186/1471-2164-12-542] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 11/02/2011] [Indexed: 11/17/2022] Open
Abstract
Background Amoebae are phagocytic protists where genetic exchanges might take place between amoeba-resistant bacteria. These amoebal pathogens are able to escape the phagocytic behaviour of their host. They belong to different bacterial phyla and often show a larger genome size than human-infecting pathogens. This characteristic is proposed to be the result of frequent gene exchanges with other bacteria that share a sympatric lifestyle and contrasts with the genome reduction observed among strict human pathogens. Results We sequenced the genome of a new amoebal pathogen, Legionella drancourtii, and compared its gene content to that of a Chlamydia-related bacterium, Parachlamydia acanthamoebae. Phylogenetic reconstructions identified seven potential horizontal gene transfers (HGTs) between the two amoeba-resistant bacteria, including a complete operon of four genes that encodes an ABC-type transporter. These comparisons pinpointed potential cases of gene exchange between P. acanthamoebae and Legionella pneumophila, as well as gene exchanges between other members of the Legionellales and Chlamydiales orders. Moreover, nine cases represent possible HGTs between representatives from the Legionellales or Chlamydiales and members of the Rickettsiales order. Conclusions This study identifies numerous gene exchanges between intracellular Legionellales and Chlamydiales bacteria, which could preferentially occur within common inclusions in their amoebal hosts. Therefore it contributes to improve our knowledge on the intra-amoebal gene properties associated to their specific lifestyle.
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Affiliation(s)
- Gregory Gimenez
- Unité des rickettsies, Faculté de Médecine, Université de la Méditerranée, Marseille, France
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Little AEF, Robinson CJ, Peterson SB, Raffa KF, Handelsman J. Rules of engagement: interspecies interactions that regulate microbial communities. Annu Rev Microbiol 2008; 62:375-401. [PMID: 18544040 DOI: 10.1146/annurev.micro.030608.101423] [Citation(s) in RCA: 260] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Microbial communities comprise an interwoven matrix of biological diversity modified by physical and chemical variation over space and time. Although these communities are the major drivers of biosphere processes, relatively little is known about their structure and function, and predictive modeling is limited by a dearth of comprehensive ecological principles that describe microbial community processes. Here we discuss working definitions of central ecological terms that have been used in various fashions in microbial ecology, provide a framework by focusing on different types of interactions within communities, review the status of the interface between evolutionary and ecological study, and highlight important similarities and differences between macro- and microbial ecology. We describe current approaches to study microbial ecology and progress toward predictive modeling.
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Affiliation(s)
- Ainslie E F Little
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, 53706, USA.
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9
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Gage DJ, Herron PM, Arango Pinedo C, Cardon ZG. Live reports from the soil grain - the promise and challenge of microbiosensors. Funct Ecol 2008. [DOI: 10.1111/j.1365-2435.2008.01464.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Schmitz-Esser S, Toenshoff ER, Haider S, Heinz E, Hoenninger VM, Wagner M, Horn M. Diversity of bacterial endosymbionts of environmental acanthamoeba isolates. Appl Environ Microbiol 2008; 74:5822-31. [PMID: 18641160 PMCID: PMC2547052 DOI: 10.1128/aem.01093-08] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 07/11/2008] [Indexed: 11/20/2022] Open
Abstract
Free-living amoebae are frequent hosts for bacterial endosymbionts. In this study, the symbionts of eight novel environmental Acanthamoeba strains isolated from different locations worldwide were characterized. Phylogenetic analysis revealed that they were related to one of four evolutionary lineages of amoeba symbionts recognized previously. This study provides evidence for the existence of only a small number of phylogenetically well-separated groups of obligate intracellular endosymbionts of acanthamoebae with global distribution.
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MESH Headings
- Acanthamoeba/genetics
- Acanthamoeba/microbiology
- Animals
- Bacteria/classification
- Bacteria/genetics
- Biodiversity
- DNA, Bacterial/genetics
- DNA, Protozoan/genetics
- Genes, Bacterial
- Genes, Protozoan
- Genes, rRNA
- Geologic Sediments/microbiology
- Molecular Sequence Data
- Phylogeny
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 18S/genetics
- Sequence Analysis, DNA
- Soil Microbiology
- Symbiosis
- Water Microbiology
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Affiliation(s)
- Stephan Schmitz-Esser
- Department of Microbial Ecology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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11
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Murase J, Noll M, Frenzel P. Impact of protists on the activity and structure of the bacterial community in a rice field soil. Appl Environ Microbiol 2006; 72:5436-44. [PMID: 16885296 PMCID: PMC1538762 DOI: 10.1128/aem.00207-06] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2006] [Accepted: 05/31/2006] [Indexed: 11/20/2022] Open
Abstract
Flooded rice fields have become a model system for the study of soil microbial ecology. In Italian rice fields, in particular, aspects from biogeochemistry to molecular ecology have been studied, but the impact of protistan grazing on the structure and function of the prokaryotic community has not been examined yet. We compared an untreated control soil with a gamma-radiation-sterilized soil that had been reinoculated with a natural bacterial assemblage. In order to verify that the observed effects were due to protistan grazing and did not result from sterilization, we set up a third set of microcosms containing sterilized soil that had been reinoculated with natural assemblage bacteria plus protists. The spatial and temporal changes in the protistan and prokaryotic communities were examined by denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analysis, respectively, both based on the small-subunit gene. Sequences retrieved from DGGE bands were preferentially affiliated with Cercozoa and other bacteriovorous flagellates. Without protists, the level of total DNA increased with incubation time, indicating that the level of the microbial biomass was elevated. Betaproteobacteria were preferentially preyed upon, while low-G + C-content gram-positive bacteria became more dominant under grazing pressure. The bacterial diversity detectable by T-RFLP analysis was greater in the presence of protists. The level of extractable NH4+ was lower and the level of extractable SO4(2-) was higher without protists, indicating that nitrogen mineralization and SO4(2-) reduction were stimulated by protists. Most of these effects were more obvious in the partially oxic surface layer (0 to 3 mm), but they could also be detected in the anoxic subsurface layer (10 to 13 mm). Our observations fit well into the overall framework developed for protistan grazing, but with some modifications pertinent to the wetland situation: O2 was a major control, and O2 availability may have limited directly and indirectly the development of protists. Although detectable in the lower anoxic layer, grazing effects were much more obvious in the partially oxic surface layer.
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Affiliation(s)
- Jun Murase
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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12
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Szillery JE, Fernandez IJ, Norton SA, Rustad LE, White AS. Using ion-exchange resins to study soil response to experimental watershed acidification. ENVIRONMENTAL MONITORING AND ASSESSMENT 2006; 116:383-98. [PMID: 16779603 DOI: 10.1007/s10661-006-7462-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 05/18/2005] [Indexed: 05/10/2023]
Abstract
Ion-exchange resins (IER) offer alternative approaches to measuring ionic movement in soils that may have advantages over traditional approaches in some settings, but more information is needed to understand how IER compare with traditional methods of measurement in forested ecosystems. At the Bear Brook Watershed in Maine (BBWM), one of two paired, forested watersheds is treated bi-monthly with S and N (28.8 and 25.2kg ha(-1)yr(-1) of S and N, respectively). Both IER and ceramic cup tension lysimeters were used to study soil solution responses after approximately 11 years of treatment. Results from both methods showed treatments resulted in the mobilization of base cations and Al, and higher SO(4)-S and inorganic N in the treated watershed. Both methods indicated similar differences in results associated with forest type (hardwoods versus softwoods), a result of differences in litter quality and atmospheric aerosol interception capacity. The correlation between lysimeter and IER data for individual analytes varied greatly. Significant correlations were evident for Na (r=0.75), Al (r=0.65), Mn (r=0.61), Fe (r=0.57), Ca (r=0.49), K (r=0.41) and NO(3)-N (r=0.59). No correlation was evident between IER and soil solution data for NH(4)-N and Pb. Both IER and soil solution techniques suggested similar interpretations of biogeochemical behavior in the watershed.
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Affiliation(s)
- Johanna E Szillery
- Department of Plant, Soil, and Environmental Sciences, University of Maine, Orono, Maine 04469, USA
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