Project description:Activating the cryptic secondary metabolic gene clusters is a vital research field in Streptomyces. The marine Streptomyces sp. FJNU027 strain which could produce tirandamycins was cultured in the oligotrophic medium. Compared with normal medium, a differential product in oligotrophic culture was found by HPLC assay. After mass fermentation, 2 mg of the differential product was obtained from 30 L fermentation broth by solvent extraction, column chromatography over sephadex LH-20 and reverse phase C18, and other methods. It was identified as 4,4',5,5'-tetramethyl-[1,1'- diphenyl]-2,2'-diol by NMR and MS data. The production of this compound was enhanced with the increment of cultural time. Transcriptome sequencing analysis showed that the highest upregulated genes under oligotrophic condition were glycosidase, TraR/DksA C4-type zinc finger protein and ribonuclease encoding genes, while the expression of a MarR family transcriptional regulator was most significantly decreased under oligotrophic condition. The results indicate that oligotrophic culture is an effective method for altering the secondary metabolism of Streptomyces.
Project description:Polyphosphate (polyP) is a ubiquitous and evolutionarily conserved form of phosphorus (P) present in all living organisms, yet its role in cellular and biogeochemical P cycling remains poorly constrained. In P-depleted marine environments, polyP consistently represents a larger fraction of total particulate P (TPP) than in P-replete environments. This P deficiency response is paradoxical under the classical view of polyP as a luxury storage compound, highlighting a longstanding unresolved discrepancy. Whether the elevated polyP:TPP ratio reflects active accumulation under P stress or simply the persistence of this intracellular pool has never been directly tested under steady-state conditions. Using continuous cultures of the globally important marine cyanobacterium Synechococcus sp. WH8102, we address this knowledge gap. While P availability strongly affected growth rates, single-cell C:N:P stoichiometry and the expression of P-stress genes, polyP:TPP increased with decreasing growth rate, reproducing the pattern observed in oligotrophic marine environments. This shift was not driven by polyP accumulation; instead, cellular polyP concentrations remained relatively stable across growth rates (ANOVA, p = 0.16), while other intracellular P pools—including RNA, free Pi, ATP and phospholipids—were preferentially depleted with decreasing P availability (ranging from 2.6- to 11.8-fold, respectively), increasing the relative contribution of polyP to total cellular P. Gene expression analysis revealed little transcription differences between polyP-metabolism associated genes. These results indicate that cellular polyP content is maintained independently of growth rate under steady-state conditions, suggesting that P deficiency responses observed in oligotrophic environments and various microorganisms in batch culture reflect slow-growing physiology (differential pool lability over selective polyP retention), with consequences for interpreting particulate P stoichiometry and export.
Project description:Marine Synechococcus, together with Prochlorococcus, contribute to a significant proportion of the primary production on Earth. The spatial distribution of these two groups of marine picocyanobacteria depends on different factors such as nutrients availability or temperature. Some Synechococcus ecotypes thrive in mesotrophic and moderately oligotrophic waters, where they exploit both oxidized and reduced forms of nitrogen. Here, we present a comprehensive study, which includes transcriptomic and proteomic analyses of the response of Synechococcus sp. strain WH7803 to nanomolar concentrations of nitrate, compared to ammonium or nitrogen starvation. We found that Synechococcus has a specific response to nanomolar nitrate concentration that differs to the response showed under nitrogen starvation or the presence of standard concentrations of either ammonium or nitrate. This fact suggests that the particular response to the uptake of nanomolar concentration of nitrate could be an evolutionary advantage for marine Synechococcus against Prochlorococcus in the natural field.
Project description:Prochlorococcus is the most abundant photosynthetic organism on Earth, contributing significantly to the global primary production and playing a prominent role in biogeochemical cycles. Prochlorococcus requires the capability to accommodate to environmental changes in order to proliferate in oligotrophic oceans, in particular regarding nitrogen availability. A precise knowledge of the composition and changes of the proteome is necessary to gain fundamental insights into such response. Here we study the effects of extreme nitrogen limitation, a feature of the oligotrophic oceans inhabited by this organism.
Project description:This study is aimed to isolate marine actinomycetes from sediments from Andaman and the Gulf of Thailand. All 101 marine actinomycetes were screened for anti-biofilm activity. Streptomyces sp. GKU223 showed significantly inhibited biofilm formation of S. aureus. The evaluation of supernatants of anti-biofilm activity produced by Streptomyces sp. GKU223 has been performed. Since the interaction between marine actinomycetes and biofilm forming bacteria has never been investigated, proteomic analysis has been used to identify whole cell proteins involved in anti–biofilm activity. Understanding the interaction at molecular level will lead to sustainably use for anti-biofilm producing marine actinomycetes in pharmaceutical and medicinal applications in the future.
Project description:This study is aimed to isolate marine actinomycetes from sediments from Andaman and the Gulf of Thailand. All 101 marine actinomycetes were screened for anti-biofilm activity. Streptomyces sp. GKU 257-1 showed significantly inhibited biofilm formation of E. coli. The evaluation of supernatants of anti-biofilm activity produced by Streptomyces sp. GKU 257-1 has been performed. Since the interaction between marine actinomycetes and biofilm forming bacteria has never been investigated, proteomic analysis has been used to identify whole cell proteins involved in anti–biofilm activity. Understanding the interaction at molecular level will lead to sustainably use for anti-biofilm producing marine actinomycetes in pharmaceutical and medicinal applications in the future.
Project description:Chlorella sp. HS2 is a halotolerant microalga exhibiting relatively high biomass productivity and substantially high lipid accumulation in marine growth media, which suggests this alga as an important crop for industrial algal cultivation systems. To determine pathways leading to HS2's acclimation responses to salt stress, we performed RNA-seq analysis with triplicated cultures grown in freshwater and marine media at both exponential and stationary growth phases. We then run de novo assembly to obtain HS2 transcriptome, which in turn was annotated and processed to extract dysregulated pathways. Results showed a large proportion of down-regulated genes, for instance photosynthesis and TCA pathways. Photosynthesis appeared, however, to recover at the stationary phase, while the general down-regulation pattern was maintained.
Project description:Although N2 fixation can occur in free-living cyanobacteria, the unicellular endosymbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) is considered to be a dominant N2-fixing species in marine ecosystems. Four UCYN-A sublineages are known from partial nitrogenase (nifH) gene sequences. However, few studies have investigated their habitat preferences and regulation by their respective hosts in open-ocean versus coastal environments. Here, we compared UCYN-A transcriptomes from oligotrophic open-ocean versus nutrient-rich coastal waters. UCYN-A1 metabolism was more impacted by habitat changes than UCYN-A2. However, across habitats and sublineages genes for nitrogen fixation and energy production were highly transcribed. Curiously these genes, critical to the symbiosis for the exchange of fixed nitrogen for fixed carbon, maintained the same schedule of diel expression across habitats and UCYN-A sublineages, including UCYN-A3 in the open-ocean transcriptomes. Our results undersore the importance of nitrogen fixation in UCYN-A symbioses across habitats, with consequences for community interaction and global biogeochemical cycles.