The Experts below are selected from a list of 14835 Experts worldwide ranked by ideXlab platform
Hanspeter Grossart - One of the best experts on this subject based on the ideXlab platform.
-
bacterial community composition associated with freshwater algae species specificity vs dependency on environmental conditions and source community
FEMS Microbiology Ecology, 2013Co-Authors: Falk Eigemann, Hanspeter Grossart, Sabine Hilt, Ivette SalkaAbstract:We studied bacterial associations with the green alga Desmodesmus armatus and the diatom Stephanodiscus minutulus under changing environmental conditions and bacterial source communities, to evaluate whether bacteria-algae associations are species-specific or more generalized and determined by external factors. Axenic and xenic algae were incubated in situ with and without allelopathically active macrophytes, and in the laboratory with sterile and nonsterile lake water and an allelochemical, tannic acid (TA). Bacterial community composition (BCC) of algae-associated bacteria was analyzed by denaturing gradient gel electrophoresis (DGGE), nonmetric multidimensional scaling, cluster analyses, and sequencing of DGGE bands. BCC of xenic algal cultures of both species were not significantly affected by changes in their environment or bacterial source community, except in the case of TA additions. Species-specific interactions therefore appear to overrule the effects of environmental conditions and source communities. The BCC of xenic and Axenic D. armatus cultures subjected to in situ bacterial colonization, however, had lower similarities (ca. 55%), indicating that bacterial precolonization is a strong factor for bacteria-algae associations irrespective of environmental conditions and source community. Our findings emphasize the ecological importance of species-specific bacteria-algae associations with important repercussions for other processes, such as the remineralization of nutrients, and organic matter dynamics.
-
effects of food on bacterial community composition associated with the copepod acartia tonsa dana
Biology Letters, 2009Co-Authors: Kam W Tang, Claudia Dziallas, Kristine Michelle L Hutalleschmelzer, Hanspeter GrossartAbstract:The estuarine copepod Acartia tonsa naturally carried diverse strains of bacteria on its body. The bacterial community composition (BCC) remained very conservative even when the copepod was fed different Axenic algal species, indicating that the food per se did not much affect BCC associated with the copepod. In xenic algal treatments, however, copepod-associated BCC differed with each alga fed, even though the same bacterial source was used to inoculate the algae. In addition, starved copepods taken at the same location but at different times significantly differed in their BCC. Algal species composition and copepod life history therefore serve to regulate BCC associated with copepods, and spatial and temporal variations in algal species composition and copepod origin would alter bacteria–copepod interactions.
Matthew W. Parrow - One of the best experts on this subject based on the ideXlab platform.
-
Axenic culture of the heterotrophic dinoflagellate pfiesteria shumwayae in a semi defined medium
Journal of Eukaryotic Microbiology, 2009Co-Authors: Hayley M Skelton, Jo Ann M. Burkholder, Matthew W. ParrowAbstract:ABSTRACT. A semi-defined, biphasic culture medium was developed that supported the Axenic growth of three strains of the heterotrophic dinoflagellate Pfiesteria shumwayae. Maximum cell yields and division rates in the semi-defined medium ranged from 0.1 × 105 to 4.0 × 105 cells/ml and 0.5 to 1.7 divisions/day, respectively, and depended on the concentration of the major components in the medium as well as the P. shumwayae strain. The medium contained high concentrations of certain dissolved and particulate organic compounds, including amino acids and lipids. Pfiesteria shumwayae flagellated cells were attracted to insoluble lipids present in the medium and appeared to feed on the lipid particles, suggesting that phagocytosis may be required for growth in Axenic culture. Development of a semi-defined medium represents significant progress toward a completely defined Axenic culture medium and subsequent determination of the biochemical requirements of P. shumwayae, needed to advance understanding of the nutritional ecology of this species. Further, this medium provides an economical, simplified method for generating high cell densities of P. shumwayae in Axenic culture that will facilitate controlled investigations on the physiology and biochemistry of this heterotrophic dinoflagellate.
-
Axenic cultivation of the heterotrophic dinoflagellate pfiesteria shumwayae and observations on feeding behavior1
Journal of Phycology, 2008Co-Authors: Hayley M Skelton, Jo Ann M. Burkholder, Matthew W. ParrowAbstract:Pfiesteria shumwayae Glasgow et J. M. Burkh. [=Pseudopfiesteria shumwayae (Glasgow et J. M. Burkh.) Litaker, Steid., P. L. Mason, Shields et P. A. Tester] is a heterotrophic dinoflagellate commonly found in temperate, estuarine waters. P. shumwayae can feed on other protists, fish, and invertebrates, but research on the biochemical requirements of this species has been restricted by the lack of Axenic cultures. An undefined, biphasic culture medium was formulated that supported the Axenic growth of two of three strains of P. shumwayae. The medium contained chicken egg yolk as a major component. Successful growth depended on the method used to sterilize the medium, and maximum cell yields (10(4) · mL(-1) ) were similar to those attained in previous research when P. shumwayae was cultured with living fish or microalgae. Additionally, P. shumwayae flagellate cells ingested particles present in the biphasic medium, allowing detailed observations of feeding behavior. This research is an initial step toward a chemically defined Axenic culture medium and determination of P. shumwayae metabolic requirements.
Anders Omsland - One of the best experts on this subject based on the ideXlab platform.
-
use of Axenic culture tools to study coxiella burnetii
Current protocols in microbiology, 2018Co-Authors: Savannah E Sanchez, Eduardo Vallejoesquerra, Anders OmslandAbstract:: Coxiella burnetii is a highly infectious obligate intracellular bacterium and the etiological agent of the zoonosis Query (Q) fever. This Gram-negative gamma-proteobacterium has adapted to replicate within a specialized compartment in mammalian phagocytic cells, known as the Coxiella-containing vacuole (CCV). Knowledge of critical characteristics of the CCV microenvironment (e.g., luminal pH), analysis of the C. burnetii genome sequence, and strategic metabolic profiling have provided the basis for determining the physicochemical and nutritional conditions necessary to support Axenic replication of C. burnetii. In this unit, the media currently utilized for Axenic culture of C. burnetii are described, with emphasis on application. To aid in experimental reproducibility and interpretation of results, considerations and limitations are discussed. Lastly, expected results for C. burnetii Axenic growth under control conditions are provided as a reference. © 2018 by John Wiley & Sons, Inc.
-
Axenic growth of coxiella burnetii
Advances in Experimental Medicine and Biology, 2012Co-Authors: Anders OmslandAbstract:Early metabolic studies of C. burnetii showed minimal metabolic activity of Axenic (host cell-free) organisms in buffers adjusted to neutral pH. However, our understanding of the organism’s physiology was greatly improved upon the discovery that C. burnetii requires an acidic pH for metabolic activation. Indeed, information gained from acid activation studies coupled with contemporary analyses using transcription microarrays, metabolic pathway reconstruction and metabolite typing, led to an Axenic culture system that supports robust growth of C. burnetii. While Axenic culture of C. burnetii can present some technical challenges, the technique is currently facilitating new lines of investigation and development of genetic tools. Axenic cultivation of C. burnetii should also prove useful in clinical settings.
Hayley M Skelton - One of the best experts on this subject based on the ideXlab platform.
-
Axenic culture of the heterotrophic dinoflagellate pfiesteria shumwayae in a semi defined medium
Journal of Eukaryotic Microbiology, 2009Co-Authors: Hayley M Skelton, Jo Ann M. Burkholder, Matthew W. ParrowAbstract:ABSTRACT. A semi-defined, biphasic culture medium was developed that supported the Axenic growth of three strains of the heterotrophic dinoflagellate Pfiesteria shumwayae. Maximum cell yields and division rates in the semi-defined medium ranged from 0.1 × 105 to 4.0 × 105 cells/ml and 0.5 to 1.7 divisions/day, respectively, and depended on the concentration of the major components in the medium as well as the P. shumwayae strain. The medium contained high concentrations of certain dissolved and particulate organic compounds, including amino acids and lipids. Pfiesteria shumwayae flagellated cells were attracted to insoluble lipids present in the medium and appeared to feed on the lipid particles, suggesting that phagocytosis may be required for growth in Axenic culture. Development of a semi-defined medium represents significant progress toward a completely defined Axenic culture medium and subsequent determination of the biochemical requirements of P. shumwayae, needed to advance understanding of the nutritional ecology of this species. Further, this medium provides an economical, simplified method for generating high cell densities of P. shumwayae in Axenic culture that will facilitate controlled investigations on the physiology and biochemistry of this heterotrophic dinoflagellate.
-
Axenic cultivation of the heterotrophic dinoflagellate pfiesteria shumwayae and observations on feeding behavior1
Journal of Phycology, 2008Co-Authors: Hayley M Skelton, Jo Ann M. Burkholder, Matthew W. ParrowAbstract:Pfiesteria shumwayae Glasgow et J. M. Burkh. [=Pseudopfiesteria shumwayae (Glasgow et J. M. Burkh.) Litaker, Steid., P. L. Mason, Shields et P. A. Tester] is a heterotrophic dinoflagellate commonly found in temperate, estuarine waters. P. shumwayae can feed on other protists, fish, and invertebrates, but research on the biochemical requirements of this species has been restricted by the lack of Axenic cultures. An undefined, biphasic culture medium was formulated that supported the Axenic growth of two of three strains of P. shumwayae. The medium contained chicken egg yolk as a major component. Successful growth depended on the method used to sterilize the medium, and maximum cell yields (10(4) · mL(-1) ) were similar to those attained in previous research when P. shumwayae was cultured with living fish or microalgae. Additionally, P. shumwayae flagellate cells ingested particles present in the biphasic medium, allowing detailed observations of feeding behavior. This research is an initial step toward a chemically defined Axenic culture medium and determination of P. shumwayae metabolic requirements.
Heesik Kim - One of the best experts on this subject based on the ideXlab platform.
-
enhancing microalgal biomass productivity by engineering a microalgal bacterial community
Bioresource Technology, 2015Co-Authors: Daehyun Cho, Rishiram Ramanan, Jina Heo, Jimin Lee, Byunghyuk Kim, Heesik KimAbstract:This study demonstrates that ecologically engineered bacterial consortium could enhance microalgal biomass and lipid productivities through carbon exchange. Phycosphere bacterial diversity analysis in xenic Chlorella vulgaris (XCV) confirmed the presence of growth enhancing and inhibiting microorganisms. Co-cultivation of Axenic C. vulgaris (ACV) with four different growth enhancing bacteria revealed a symbiotic relationship with each bacterium. An artificial microalgal-bacterial consortium (AMBC) constituting these four bacteria and ACV showed that the bacterial consortium exerted a statistically significant (P<0.05) growth enhancement on ACV. Moreover, AMBC had superior flocculation efficiency, lipid content and quality. Studies on carbon exchange revealed that bacteria in AMBC might utilize fixed organic carbon released by microalgae, and in return, supply inorganic and low molecular weight (LMW) organic carbon influencing algal growth and metabolism. Such exchanges, although species specific, have enormous significance in carbon cycle and can be exploitated by microalgal biotechnology industry.
-
novel approach for the development of Axenic microalgal cultures from environmental samples
Journal of Phycology, 2013Co-Authors: Daehyun Cho, Rishiram Ramanan, Jimin Lee, Byunghyuk Kim, Sora Kim, Chan Yoo, Gangguk Choi, Heesik KimAbstract:We demonstrated a comprehensive approach for development of Axenic cultures of microalgae from environmental samples. A combination of ultrasonication, fluorescence-activated cell sorting (FACS), and micropicking was used to isolate Axenic cultures of Chlorella vulgaris Beyerinck (Beijerinck) and Chlorella sorokiniana Shihira & R.W. Krauss from swine wastewater, and Scenedesmus sp. YC001 from an open pond. Ultrasonication dispersed microorganisms attached to microalgae and reduced the bacterial population by 70%, and when followed by cell sorting yielded 99.5% pure microalgal strains. The strains were rendered Axenic by the novel method of micropicking and were tested for purity in both solid and liquid media under different trophic states. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene confirmed the absence of unculturable bacteria, whereas fluorescence microscopy and scanning electron microscopy (SEM) further confirmed the Axenicity. This is the most comprehensive approach developed to date for obtaining Axenic microalgal strains without the use of antibiotics and repetitive subculturing.
-
microalgae associated bacteria play a key role in the flocculation of chlorella vulgaris
Bioresource Technology, 2013Co-Authors: Jimi Lee, Daehyu Cho, Rishiram Ramana, Yunghyuk Kim, Heesik KimAbstract:Flocculation is most preferred method for harvesting microalgae, however, the role of bacteria in microalgal flocculation process is still unknown. This study proves that bacteria play a profound role in flocculating by increasing the floc size resulting in sedimentation of microalgae. A flocculating activity of 94% was achieved with xenic Chlorella vulgaris culture as compared to 2% achieved with Axenic culture. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene of xenic C. vulgaris culture revealed the presence of Flavobacterium sp., Terrimonas sp., Sphingobacterium sp., Rhizobium sp. and Hyphomonas sp. as microalgae-associated bacteria. However when Flavobacterium, Terrimonas, Sphingobacterium were eliminated by fluorescence activated cell sorter (FACS), flocculating activity reduced to 3%. Further studies with cell free extracts also suggest that bacterial extracellular substances might also have a role in enhancing flocculation. We conclude that the collective presence of certain bacteria is the determining factor in flocculation of C. vulgaris.
