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  • Bacterial diversity  (1)
  • Cell density  (1)
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  • 1
    ISSN: 1432-072X
    Keywords: Alcaligenes eutrophus ; PHB ; Cell volume ; Cell density ; Percoll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Accumulation of poly-β-hydroxybutyrate (PHB) was studied in Alcaligenes eutrophus strain N9A. Under nitrogen limitation and heterotrophic conditions, the cells accumulated PHB at a rate of 50 fg cell-1 h-1. Volume increased from 1.208 to 3.808 μm3 and buoyant density from 1.110 to 1.145 pg μm-3 with an increase in PHB from 0 up to 1.699 pg cell-1. Volume was found to change linearly with PHB content. The changes were due to increases in cell width and not in cell length. PHB explained 93% of the changes in cellular volume. The relationship between density and PHB was hyperbolic. PHB explained 96% of the changes in density. When a mutant strain unable to accumulate PHB was analyzed together with the wild type, the PHB-less mutant and the wild type showed densities of 1.100 pg μm-3 and 1.120 pg μm-3, respectively, in gradients of 65% Percoll. In sucrose gradients, nevertheless, the results were reversed. This discrepancy was explained by the high osmolarity of sucrose which gives artificial results. Thus, we conclude that Percoll is a more suitable medium than sucrose to measure the density of live bacterial cells.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2010. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbila Ecology 61 (2010): 221-233, doi:10.3354/ame01484.
    Description: Due to analytical limitations, patterns of richness and evenness of microbes are scarce in the current literature. The newest and powerful pyrosequencing technology may solve this issue by sampling thousands of sequences from the same community. We conducted a study of diversity along a horizontal transect (ca. 120 km) and a depth profile (surface to bottom at ca. 2000 m) in the northwestern Mediterranean Sea, using this technology on the V6 region of the 16S rDNA gene and analyzed patterns of richness and evenness of marine free-living bacterial communities. A total of 201605 tag sequences were obtained from the 10 samples considered and clustered according to their similarity in 1200 operational taxonomic units (OTUs) per sample on average. We found a parallel decrease in richness and evenness from coast to offshore and from bottom to surface. We also observed a predominance of a few OTUs in each sample, while ca. 50% of all OTUs were found as singletons, which indicated that the community structures differed dramatically between sites despite the relative proximity and the physical connectivity between the samples. Despite these differences, using the 300 most abundant OTUs only was sufficient to obtain the same clustering of samples as with the complete dataset. Finally, both richness and evenness were negatively correlated with bacterial biomass and heterotrophic production.
    Description: The Modivus cruise was supported by the Spanish MICINN project MODIVUS (CTM2005-04795/ MAR). Additional work was supported by a Spanish MICINN grant GEMMA (CTM2007-63753-C02-01/MAR).
    Keywords: Bacterial diversity ; Pyrosequencing ; Blanes Bay Microbial Observatory
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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