SEARCH · PubMed Health

Results for “Prochlorococcus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed2006

Aerobic anoxygenic phototrophic bacteria in the Mid-Atlantic Bight and the North Pacific Gyre.

The abundance of aerobic anoxygenic phototrophic (AAP) bacteria, cyanobacteria, and heterotrophs was examined in the Mid-Atlantic Bight and the central North Pacific Gyre using infrared fluorescence microscopy coupled with image analysis and flow cytometry. AAP bacteria comprised 5% to 16% of total prokaryotes in the Atlantic Ocean but only 5% or less in the Pacific Ocean. In the Atlantic, AAP bacterial abundance was as much as 2-fold higher than that of Prochlorococcus spp. and 10-fold higher than that of Synechococcus spp. In contrast, Prochlorococcus spp. outnumbered AAP bacteria 5- to 50-fold in the Pacific. In both oceans, subsurface abundance maxima occurred within the photic zone, and AAP bacteria were least abundant below the 1% light depth. The abundance of AAP bacteria rivaled some groups of strictly heterotrophic bacteria and was often higher than the abundance of known AAP bacterial genera (Erythrobacter and Roseobacter spp.). Concentrations of bacteriochlorophyll a (BChl a) were low ( approximately 1%) compared to those of chlorophyll a in the North Atlantic. Although the BChl a content of AAP bacteria per cell was typically 20- to 250-fold lower than the divinyl-chlorophyll a content of Prochlorococcus, the pigment content of AAP bacteria approached that of Prochlorococcus in shelf break water. Our results suggest that AAP bacteria can be quite abundant in some oceanic regimes and that their distribution in the water column is consistent with phototrophy.

Aerobiosis↗

PubMed2005

Accelerated evolution associated with genome reduction in a free-living prokaryote.

BACKGROUND: Three complete genomes of Prochlorococcus species, the smallest and most abundant photosynthetic organism in the ocean, have recently been published. Comparative genome analyses reveal that genome shrinkage has occurred within this genus, associated with a sharp reduction in G+C content. As all examples of genome reduction characterized so far have been restricted to endosymbionts or pathogens, with a host-dependent lifestyle, the observed genome reduction in Prochlorococcus is the first documented example of such a process in a free-living organism. RESULTS: Our results clearly indicate that genome reduction has been accompanied by an increased rate of protein evolution in P. marinus SS120 that is even more pronounced in P. marinus MED4. This acceleration has affected every functional category of protein-coding genes. In contrast, the 16S rRNA gene seems to have evolved clock-like in this genus. We observed that MED4 and SS120 have lost several DNA-repair genes, the absence of which could be related to the mutational bias and the acceleration of amino-acid substitution. CONCLUSIONS: We have examined the evolutionary mechanisms involved in this process, which are different from those known from host-dependent organisms. Indeed, most substitutions that have occurred in Prochlorococcus have to be selectively neutral, as the large size of populations imposes low genetic drift and strong purifying selection. We assume that the major driving force behind genome reduction within the Prochlorococcus radiation has been a selective process favoring the adaptation of this organism to its environment. A scenario is proposed for genome evolution in this genus.

Adaptation, Physiological↗

PubMed2005

On-board flow cytometric observation of picoplankton community structure in the East China Sea during the fall of different years.

On-board flow cytometric determinations of picoplankton abundance (i.e. Synechococcus spp., Prochlorococcus spp., picoeukaryotes and also heterotrophic bacteria) were obtained in the East China Sea in fall of 2000 and 2003. The average abundances of Synechococcus, Prochlorococcus, picoeukaryotes and heterotrophic bacteria were 10(5), 10(5), 10(4) and 10(6) cells ml(-1), respectively. Synechococcus, picoeukaryotes and heterotrophic bacteria were abundant at all the stations and presented higher concentration in the inner shelf where influences from the Changjiang effluent plumes and the coastal upwelling were evident, while Prochlorococcus was absent from the near-shore stations and became the dominant picophytoplankton population in offshore waters, where its abundance was comparable to that for heterotrophic bacteria. All picoplankton groups showed a reduction in cell number with depth, and a positive correlation with water temperature were observed, which reflected the importance of light and temperature on picoplankton growth. A negative relationship with salinity was found for heterotrophic bacteria along two sections across the East China Sea Shelf, and distribution of picoplankton was dominated by different water masses. The fixation could lead to loss in Prochlorococcus cell numbers within one month, and all the picoplankton numbers decreased dramatically after three months.

Biodiversity↗

PubMed2000

Multiplication of antenna genes as a major adaptation to low light in a marine prokaryote.

Two ecotypes of the prokaryote Prochlorococcus adapted to distinct light niches in the ocean have been described recently. These ecotypes are characterized by their different (divinyl-) chlorophyll (Chl) a to Chl b ratios and 16S rRNA gene signatures, as well as by their significantly distinct irradiance optima for growth and photosynthesis [Moore, L. R., Rocap, G. & Chisholm, S. W. (1998) Nature (London) 393, 464-467]. However, the molecular basis of their physiological differences remained, so far, unexplained. In this paper, we show that the low-light-adapted Prochlorococcus strain SS120 possesses a gene family of seven transcribed genes encoding different Chl a/b-binding proteins (Pcbs). In contrast, Prochlorococcus sp. MED4, a high-light-adapted ecotype, possesses a single pcb gene. The presence of multiple antenna genes in another low-light ecotype (NATL2a), but not in another high-light ecotype (TAK9803-2), is demonstrated. Thus, the multiplication of pcb genes appears as a key factor in the capacity of deep Prochlorococcus populations to survive at extremely low photon fluxes.

Amino Acid Sequence↗

PubMed2004

Natural community structure of cyanobacteria in the South China Sea as revealed by rpoC1 gene sequence analysis.

AIMS: To examine the community structure of cyanobacterial populations of the South China Sea on the surface and at depth of 80 m. METHODS AND RESULTS: Direct PCR amplification of RNA polymerase (rpoC1) genes from environmental DNAs extracted from seawater, and cloning of the fragments and sequence analysis were used. A great diversity of Prochlorococcus and Synechococcus were detected at the investigation site. Genetically related Prochlorococcus were found in both layers while Synechococcus were found only on the surface. Prochlorococcus were clustered with the known high-light adapted II genotypes, and further divided into seven groups. Synechococcus could be divided into two groups, and the second group could be further subdivided into several clades. CONCLUSION: The dominant genotype of Prochlorococcus was high-light adapted II genotype, and Synechococcus were distributed basically on the surface. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report about the cyanobacterial community structure in the South China Sea, and an important supplement to the current understanding of the relationship between genetic and ecological diversity and environments.

China↗

PubMed2002

Analysis of the hli gene family in marine and freshwater cyanobacteria.

Certain cyanobacteria thrive in natural habitats in which light intensities can reach 2000 micromol photon m(-2) s(-1) and nutrient levels are extremely low. Recently, a family of genes designated hli was demonstrated to be important for survival of cyanobacteria during exposure to high light. In this study we have identified members of the hli gene family in seven cyanobacterial genomes, including those of a marine cyanobacterium adapted to high-light growth in surface waters of the open ocean (Prochlorococcus sp. strain Med4), three marine cyanobacteria adapted to growth in moderate- or low-light (Prochlorococcus sp. strain MIT9313, Prochlorococcus marinus SS120, and Synechococcus WH8102), and three freshwater strains (the unicellular Synechocystis sp. strain PCC6803 and the filamentous species Nostoc punctiforme strain ATCC29133 and Anabaena sp. [Nostoc] strain PCC7120). The high-light-adapted Prochlorococcus Med4 has the smallest genome (1.7 Mb), yet it has more than twice as many hli genes as any of the other six cyanobacterial species, some of which appear to have arisen from recent duplication events. Based on cluster analysis, some groups of hli genes appear to be specific to either marine or freshwater cyanobacteria. This information is discussed with respect to the role of hli genes in the acclimation of cyanobacteria to high light, and the possible relationships among members of this diverse gene family.

Amino Acid Sequence↗

PubMed1994

Cyanobacterial community structure as seen from RNA polymerase gene sequence analysis.

PCR was used to amplify DNA-dependent RNA polymerase gene sequences specifically from the cyanobacterial population in a seawater sample from the Sargasso Sea. Sequencing and analysis of the cloned fragments suggest that the population in the sample consisted of two distinct clusters of Prochlorococcus-like cyanobacteria and four clusters of Synechococcus-like cyanobacteria. The diversity within these clusters was significantly different, however. Clones within each Synechococcus-like cluster were 99 to 100% identical, while each Prochlorococcus-like cluster was only 91% identical at the nucleotide level. One Prochlorococcus-like cluster was significantly more closely related to a Mediterranean Sea (surface) Prochlorococcus isolate than to the other cluster, showing the highly divergent nature of this group even in one sample. The approach described here can be used as a general method for examining cyanobacterial diversity, while an oligotrophic ocean ecosystem such as the Sargasso Sea may be an ideal model for examining diversity in relation to environmental parameters.

Base Sequence↗

PubMed2005

Time series observation based InfraRed Epifluorescence Microscopic (TIREM) approach for accurate enumeration of bacteriochlorophyll-containing microbes in marine environments.

Bacteriochlorophyll a Containing Microbes (BCM) are a unique group of microorganisms in the marine environment. Accurate determination of their abundance is critical for understanding their role in energy flow and carbon cycle in the ecosystem. The InfraRed Epifluorescence Microscopy (IREM) method, using infrared fluorescence as the diagnostic signal of BCM, is the most convenient means to date for enumeration of BCM in seawater, but IREM methodology suffers from serious errors introduced by cyanobacteria, which also can emit infrared fluorescence and whose abundance is of the same order of magnitude as BCM. In the present study, an advanced "Time-series observation based cyanobacteria-calibrated InfraRed Epifluorescence Microscopy (TIREM)" approach is established for accurate enumeration of BCM in marine environments. The protocol is distinguished by its use of time series observation, auto-imaging and digital analysis. In principle, the correct count of BCM can be obtained by subtracting the cyanobacterial count from the total infrared positive count. The challenge, however, is that Prochlorococcus, the most abundant cyanobacterium in the sea, is readily visible in infrared images but not visible in the initial cyanobacterial images obtained by epifluorescence microscopy because its emission signals are masked by brighter fluorescence from larger cells like Synechococcus coexisting in seawater samples. Prochlorococcus cells become gradually visible when the fluorescence from Synechococcus cells declines after a period of exposure to excitation light. Therefore the plateau (maximum) count of the cyanobacterial cells in time series images rather than in the initial ones, as previously believed, represents the correct count for the total number of cyanobacteria (Synechococcus plus Prochlorococcus cells). Thus, the accurate estimation of BCM abundance can only be calculated from the formula: [BCM cells] = [plateau count of infrared positive cells]-[plateau count of cyanobacterial cells]. The conceptual advance of the TIREM protocol is that in classical epifluorescence microscopy or in IREM protocols, quick observation is recommended to avoid quenching the fluorescence, but in the TIREM protocol, instead, time series observation is the key for obtaining reliable data. The TIREM protocol is validated by studies using BCM and cyanobacterial pure cultures as well as by examination of samples from various marine environments.

Bacteriochlorophylls↗

PubMed2006

Sulfolipids dramatically decrease phosphorus demand by picocyanobacteria in oligotrophic marine environments.

There is growing evidence that dissolved phosphorus can regulate planktonic production in the oceans' subtropical gyres, yet there is little quantitative information about the biochemical fate of phosphorus in planktonic communities. We observed in the North Pacific Subtropical Gyre (NPSG) that the synthesis of membrane lipids accounted for 18-28% of the phosphate (PO4(3-)) taken up by the total planktonic community. Paradoxically, Prochlorococcus, the cyanobacterium that dominates NPSG phytoplankton, primarily synthesizes sulfoquinovosyldiacylglycerol (SQDG), a lipid that contains sulfur and sugar instead of phosphate. In axenic cultures of Prochlorococcus, it was observed that <1% of the total PO4(3-) uptake was incorporated into membrane lipids. Liquid chromatography/mass spectrometry of planktonic lipids in the NPSG confirmed that SQDG was the dominant membrane lipid. Furthermore, the analyses of SQDG synthesis genes from the Sargasso Sea environmental genome showed that the use of sulfolipids in subtropical gyres was confined primarily to picocyanobacteria; no sequences related to known heterotrophic bacterial SQDG lineages were found. This biochemical adaptation by Prochlorococcus must be a significant benefit to these organisms, which compete against phospholipid-rich heterotrophic bacteria for PO4(3-). Thus, evolution of this "sulfur-for-phosphorus" strategy set the stage for the success of picocyanobacteria in oligotrophic environments and may have been a major event in Earth's early history when the relative availability of sulfate and PO4(3-) were significantly different from today's ocean.

Chromatography, High Pressure Liquid↗

PubMed2005

Coupling 16S-ITS rDNA clone libraries and automated ribosomal intergenic spacer analysis to show marine microbial diversity: development and application to a time series.

We outline an approach to simultaneously assess multilevel microbial diversity patterns utilizing 16S-ITS rDNA clone libraries coupled with automated ribosomal intergenic spacer analysis (ARISA). Sequence data from 512 clones allowed estimation of ARISA fragment lengths associated with bacteria in a coastal marine environment. We matched 92% of ARISA peaks (each comprising >1% total amplified product) with corresponding lengths from clone libraries. These peaks with putative identification accounted for an average of 83% of total amplified community DNA. At 16S rDNA similarities <98%, most taxa displayed differences in ARISA fragment lengths >10 bp, readily detectable and suggesting ARISA resolution is near the 'species' level. Prochlorococcus abundance profiles from ARISA were strongly correlated (r2=0.86) to Prochlorococcus cell counts, indicating ARISA data are roughly proportional to actual cell abundance within a defined taxon. Analysis of ARISA profiles for 42 months elucidated patterns of microbial presence and abundance providing insights into community shifts and ecological niches for specific organisms, including a coupling of ecological patterns for taxa within the Prochlorococcus, the Gamma Proteobacteria and Actinobacteria. Clade-specific ARISA protocols were developed for the SAR11 and marine cyanobacteria to resolve ambiguous identifications and to perform focused studies. 16S-ITS data allowed high-resolution identification of organisms by ITS sequence analysis, and examination of microdiversity.

Automation↗

PubMed2005

The occurrence of rapidly reversible non-photochemical quenching of chlorophyll a fluorescence in cyanobacteria.

Cyanobacteria have previously been considered to differ fundamentally from plants and algae in their regulation of light harvesting. We show here that in fact the ecologically important marine prochlorophyte, Prochlorococcus, is capable of forming rapidly reversible non-photochemical quenching of chlorophyll a fluorescence (NPQf or qE) as are freshwater cyanobacteria when they employ the iron stress induced chlorophyll-based antenna, IsiA. For Prochlorococcus, the capacity for NPQf is greater in high light-adapted strains, except during iron starvation which allows for increased quenching in low light-adapted strains. NPQf formation in freshwater cyanobacteria is accompanied by deep Fo quenching which increases with prolonged iron starvation.

Bacterial Proteins↗

PubMed2005

Photosynthesis genes in marine viruses yield proteins during host infection.

Cyanobacteria, and the viruses (phages) that infect them, are significant contributors to the oceanic 'gene pool'. This pool is dynamic, and the transfer of genetic material between hosts and their phages probably influences the genetic and functional diversity of both. For example, photosynthesis genes of cyanobacterial origin have been found in phages that infect Prochlorococcus and Synechococcus, the numerically dominant phototrophs in ocean ecosystems. These genes include psbA, which encodes the photosystem II core reaction centre protein D1, and high-light-inducible (hli) genes. Here we show that phage psbA and hli genes are expressed during infection of Prochlorococcus and are co-transcribed with essential phage capsid genes, and that the amount of phage D1 protein increases steadily over the infective period. We also show that the expression of host photosynthesis genes declines over the course of infection and that replication of the phage genome is a function of photosynthesis. We thus propose that the phage genes are functional in photosynthesis and that they may be increasing phage fitness by supplementing the host production of these proteins.

Bacteriophages↗

PubMed2024

A distinct, high-affinity, alkaline phosphatase facilitates occupation of P-depleted environments by marine picocyanobacteria.

Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus, the two most abundant phototrophs on Earth, thrive in oligotrophic oceanic regions. While it is well known that specific lineages are exquisitely adapted to prevailing in situ light and temperature regimes, much less is known of the molecular machinery required to facilitate occupancy of these low-nutrient environments. Here, we describe a hitherto unknown alkaline phosphatase, Psip1, that has a substantially higher affinity for phosphomonoesters than other well-known phosphatases like PhoA, PhoX, or PhoD and is restricted to clade III Synechococcus and a subset of high light I-adapted Prochlorococcus strains, suggesting niche specificity. We demonstrate that Psip1 has undergone convergent evolution with PhoX, requiring both iron and calcium for activity and likely possessing identical key residues around the active site, despite generally very low sequence homology. Interrogation of metagenomes and transcriptomes from TARA oceans and an Atlantic Meridional transect shows that psip1 is abundant and highly expressed in picocyanobacterial populations from the Mediterranean Sea and north Atlantic gyre, regions well recognized to be phosphorus (P)-deplete. Together, this identifies psip1 as an important oligotrophy-specific gene for P recycling in these organisms. Furthermore, psip1 is not restricted to picocyanobacteria and is abundant and highly transcribed in some α-proteobacteria and eukaryotic algae, suggesting that such a high-affinity phosphatase is important across the microbial taxonomic world to occupy low-P environments.

Alkaline Phosphatase↗

PubMed2006

Prevalence and evolution of core photosystem II genes in marine cyanobacterial viruses and their hosts.

Cyanophages (cyanobacterial viruses) are important agents of horizontal gene transfer among marine cyanobacteria, the numerically dominant photosynthetic organisms in the oceans. Some cyanophage genomes carry and express host-like photosynthesis genes, presumably to augment the host photosynthetic machinery during infection. To study the prevalence and evolutionary dynamics of this phenomenon, 33 cultured cyanophages of known family and host range and viral DNA from field samples were screened for the presence of two core photosystem reaction center genes, psbA and psbD. Combining this expanded dataset with published data for nine other cyanophages, we found that 88% of the phage genomes contain psbA, and 50% contain both psbA and psbD. The psbA gene was found in all myoviruses and Prochlorococcus podoviruses, but could not be amplified from Prochlorococcus siphoviruses or Synechococcus podoviruses. Nearly all of the phages that encoded both psbA and psbD had broad host ranges. We speculate that the presence or absence of psbA in a phage genome may be determined by the length of the latent period of infection. Whether it also carries psbD may reflect constraints on coupling of viral- and host-encoded PsbA-PsbD in the photosynthetic reaction center across divergent hosts. Phylogenetic clustering patterns of these genes from cultured phages suggest that whole genes have been transferred from host to phage in a discrete number of events over the course of evolution (four for psbA, and two for psbD), followed by horizontal and vertical transfer between cyanophages. Clustering patterns of psbA and psbD from Synechococcus cells were inconsistent with other molecular phylogenetic markers, suggesting genetic exchanges involving Synechococcus lineages. Signatures of intragenic recombination, detected within the cyanophage gene pool as well as between hosts and phages in both directions, support this hypothesis. The analysis of cyanophage psbA and psbD genes from field populations revealed significant sequence diversity, much of which is represented in our cultured isolates. Collectively, these findings show that photosynthesis genes are common in cyanophages and that significant genetic exchanges occur from host to phage, phage to host, and within the phage gene pool. This generates genetic diversity among the phage, which serves as a reservoir for their hosts, and in turn influences photosystem evolution.

Base Composition↗

PubMed2003

Toward an understanding of cell growth and the cell division cycle of unicellular photoautotrophic cyanobacteria.

The cell division cycle of Synechococcus sp. strain PCC 6301 in light is characterized by the sequential and orderly appearance of macromolecular synthesis periods. In the dark, macromolecular synthesis and cell division are severely curtailed. When dark-incubated cultures are reexposed to light, a new cell cycle is initiated. The pattern of the cell events displayed by Synechococcus in light and the absence of sustained growth in dark incubation conditions suggests that light-activated regulatory molecules control macromolecular synthesis and the cell division cycle. For example, ribosomal RNA synthesis is stimulated by a light-activated DNA binding factor in light but not in the dark. Light/dark conditions induce cell synchrony in Prochlorococcus. Distinct G1, S and G2 phases characterize cell cycles of marine Synechococcus and Prochlorococcus. Cell division in Synechococcus elongatus PCC 7942 and marine Synechococcus is controlled by circadian oscillators.

Cell Cycle↗

PubMed1992

Multiple evolutionary origins of prochlorophytes within the cyanobacterial radiation.

The taxonomic group Prochlorales (Lewin 1977) Burger-Wiersma, Stal and Mur 1989 was established to accommodate a set of prokaryotic oxygenic phototrophs which, like plant, green algal and euglenoid chloroplasts, contain chlorophyll b instead of phycobiliproteins. Prochlorophytes were originally proposed (with concomitant scepticism) to be a monophyletic group sharing a common ancestry with these 'green' chloroplasts. Results from molecular sequence phylogenies, however, have suggested that Prochlorothrix hollandica is not on a lineage that leads to plastids. Our results from 16S ribosomal RNA sequence comparisons, which include new sequences from the marine picoplankter Prochlorococcus marinus and the Lissoclinum patella symbiont Prochloron sp., indicate that prochlorophytes are polyphyletic within the cyanobacterial radiation, and suggest that none of the known species is specifically related to chloroplasts. This implies that the three prochlorophytes and the green chloroplast ancestor acquired chlorophyll b and its associated structural proteins in convergent evolutionary events. We report further that the 16S rRNA gene sequence from Prochlorococcus is very similar to those of open ocean Synechococcus strains (marine cluster A), and to a family of 16S rRNA genes shotgun-cloned from plankton in the north Atlantic and Pacific Oceans.

Base Sequence↗

PubMed1996

Coexistence of phycoerythrin and a chlorophyll a/b antenna in a marine prokaryote.

Prochlorococcus marinus CCMP 1375, a ubiquitous and ecologically important marine prochlorophyte, was bound to possess functional genes coding for the alpha and beta subunits of a phycobiliprotein. The latter is similar to phycoerythrins (PE) from marine Synechococcus cyanobacteria and bind a phycourobilin-like pigment as the major chromophore. However, differences in the sequences of the alpha and beta chains compared with known PE subunits and the presence of a single bilin attachment site on the alpha subunit designate it as a novel PE type, which we propose naming PE-III. P. marinus is the sole prokaryotic organisms known so far that contains chlorophylls a and b as well as phycobilins. These data strongly suggest that the common ancestor of prochlorophytes and the Synechococcus cyanobacteria contained phycobilins. Flow cytometric data from the tropical Pacific Ocean provide evidence that deep populations of Prochlorococcus possess low amounts of a PE-like pigment, which could serve either in light harvesting or nitrogen storage or both.

Amino Acid Sequence↗

PubMed1997

An immunological approach to detect phosphate stress in populations and single cells of photosynthetic picoplankton.

In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associated phosphate-binding protein specifically synthesized under conditions of restricted inorganic phosphate (P1) availability (D. J. Scanlan, N. H. Mann, and N. G. Carr, Mol. Microbiol. 10:181-191, 1993). We have assessed its use as a potential diagnostic marker for the P status of photosynthetic picoplankton. Expression of PstS in Synechococcus sp. strain WH7803 was observed when the P1 concentration fell below 50 nM, demonstrating that the protein is induced at concentrations of P1 typical of oligotrophic conditions. PstS expression could be specifically detected by use of standard Western blotting (immunoblotting) techniques in natural mesocosm samples under conditions in which the N/P ratio was artificially manipulated to force P depletion. In addition, we have developed an immunofluorescence assay that can detect PstS expression in single Synechococcus cells both in laboratory cultures and natural samples. We show that antibodies raised against PstS cross-react with P-depleted Prochlorococcus cells, extending the use of these antibodies to both major groups of prokaryotic photosynthetic picoplankton. Furthermore, DNA sequencing of a Prochlorococcus pstS homolog demonstrated high amino acid sequence identity (77%) with the marine Synechococcus sp. strain WH7803 protein, including those residues in Escherichia coli PstS known to be directly involved in phosphate binding.

Carrier Proteins↗