Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Impact of a heterotroph, Alteromonas MIT1002, on the transcriptome of Prochlorococcus NATL2A

ABSTRACT: We examine how the transcriptome of Prochlorococcus strain NATL2A changes in the presence of a naturally co-occurring heterotroph, Alteromonas macleodii MIT1002. Significant changes in the Prochlorococcus transcriptome were evident within six hours of co-culture, with groups of transcripts changing in different temporal waves. Many transcriptional changes persisted throughout the 48-hour experiment, indicating that the presence of the heterotroph affected a stable shift in Prochlorococcus physiology. These initial transcriptome changes largely correspond to reduced stress conditions within Prochlorococcus, as inferred from decreases in relative abundance for transcripts encoding DNA repair enzymes and many members of the âhigh-light inducibleâ family of stress response proteins. Notable changes were also seen in transcripts encoding components of the photosynthetic apparatus (particularly an increase in PSI subunits and chlorophyll synthesis enzymes), ribosomal proteins and biosynthetic enzymes. Changes in secretion-related proteins and transporters also highlight the potential for metabolic exchange between the two strains. At each of 7 timepoints, samples from 3 biological replicate co-cultures are compared to 3 biological replicate axenic Prochlorococcus cultures that serve as a control.

ORGANISM(S): Prochlorococcus marinus str. NATL2A

SUBMITTER: Steven Biller

PROVIDER: E-GEOD-73511 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:RNA decay was measured in Prochlorococcus after inhibition of transcription by rifampicin using customized Affymetrix gene expression arrays. RNA turnover plays an important role in the gene regulation of microorganisms and influences their speed of acclimation to environmental changes. We investigated whole-genome RNA stability of Prochlorococcus, a relatively slow-growing marine cyanobacterium doubling approximately once a day, which is extremely abundant in the oceans. Using a combination of microarrays, quantitative RT-PCR and a new algorithm for determining RNA decay rates, we found a median half-life of 2.4 min and a median decay rate of 2.6 min for expressed genes â two-fold faster than that reported for any organism. The shortest transcript half-life (33 seconds) was for a gene of unknown function, while some of the longest (ca. 18 min) were for highly expressed genes. Genes organized in operons displayed intriguing mRNA decay patterns, such as increased stability, and delayed onset of decay with greater distance from the transcriptional start site. The same phenomenon was observed on a single probe resolution for genes greater than 2 kb. We hypothesize that the fast turnover relative to generation time in Prochlorococcus may enable a swift response to environmental changes through rapid recycling of nucleotides, which could be advantageous in nutrient poor oceans. Our growing understanding of RNA half-lives will inform on the modelling of cell processes and help interpret the growing bank of metatranscriptomic studies of wild populations of Prochlorococcus. The surprisingly complex decay patterns of large transcripts reported here, and the method developed to describe them, will open new avenues for the investigation and understanding of RNA decay for all organisms. Prochlorococcus cells were treated with rifampicin, which prevents initiation of new transcripts. Cells were harvested at 0 min (before rifampicin addition), 2.5 min, 5 min, 10 min, 20 min, 40 min and 60 min after rifampicin addition.

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Impact of a heterotroph, Alteromonas MIT1002, on the transcriptome of Prochlorococcus NATL2A

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