Project description:Light was a ubiquitous environmental stimulus. Deep-sea microorganisms were exposed to a pervasive blue light optical environment. The utilization of blue light by deep-sea microorganisms, especially non-photosynthetic microorganisms, and the downstream pathway after light reception were obscure. Under the enrichment condition surrounded by blue light, a potential novel species named Spongiibacter nanhainus CSC3.9 from the deep-sea cold seep was isolated. Its growth and metabolism under blue light were significantly better than other wavelengths of light. Six blue light sensing proteins, including four BLUF (Blue Light Using Flavin) and two bacteriophytochrome, were annotated in the genome of strain CSC3.9. Then, with the assist of proteomic analysis, we demonstrated that 15960-BLUF was a crucial blue light receptor that interfered with motor behavior through chemotaxis pathway by means of in vivo and in vitro verification. In addition, 15960-BLUF mediated part of the blue light to promote the growth of strain CSC3.9. Further, we summarized the functional BLUF proteins from isolated marine microorganisms, and the high abundance distribution of BLUF similar to the downstream unresponsive domain type in strain CSC3.9 was demonstrated. The widespread distribution of BLUF protein in marine bacteria implied the extensiveness of this regulatory mechanism, and wavelength variation of light was a potential means to isolate uncultured microorganisms. This was the first reported in deep-sea microorganisms that BLUF-dependent physiological response to blue light. It provided a new clue for the blue light adaptation of microorganisms in disphotic zone.
Project description:Low temperature is the most wide-spread “hostile” environmental factor on earth while at the same time the most common condition for marine organisms. However, the unique adaptive mechanisms that enable the survival of marine microorganisms under low temperature are unclear. Since low temperature is always accompanied by high pressure and other adverse conditions in marine environment, here we studied the metabolic adaptation of a marine strain to prolonged low temperature under high pressure. The strain studied is a psychrotolerant Microbacterium sediminis isolated from deep sea sediment. By using 1H nuclear magnetic resonance (NMR)-based metabolomics approach, we detected the spectral data of polar extracts of the strain M. sediminis, and applied multivariate statistical analysis methods together with univariate analysis to analyze metabolic profiles associated to different conditions. The metabolic profiles of the M. sediminis strain cultivated under high pressure at low temperature were distinctly different from those cultivated under high pressure at normal temperature. We identified the differential metabolites which were responsible for distinguishing the metabolic profiles and compared their relative intensities between groups. We also compared the different adaptive responses of the strain at different growth stages to the prolonged low temperature under high pressure. We proposed that the low-temperature adapting process of the M. sediminis strain involves, 1) the regulation of osmotic pressure using amino acids as possible alternative osmolytes, and, 2) the strengthen of glycolysis and the maintenance of TCA cycle via amino acids anaplerotic reaction. We put forward that the main difference of adaptation to low temperature for the strain at different growth stages was related to energy metabolism. Our findings improved the understanding of the low-temperature adaptive mechanisms for marine microorganisms under high pressure on the metabolic level.
Project description:Iron-sulfur minerals such as pyrite are found in many marine benthic habitats. At deep-sea hydrothermal vent sites they occur as massive sulfide chimneys. Hydrothermal chimneys formed by mineral precipitation from reduced vent fluids upon mixing with cold oxygenated sea water. While microorganisms inhabiting actively venting chimneys and utilizing reduced compounds dissolved in the fluids for energy generation are well studied, only little is known about the microorganisms inhabiting inactive sulfide chimneys. We performed a comprehensive meta-proteogenomic analysis combined with radiometric dating to investigate the diversity and function of microbial communities found on inactive sulfide chimneys of different ages from the Manus Basin (SW Pacific). Our study sheds light on potential lifestyles and ecological niches of yet poorly described bacterial clades dominating inactive chimney communities.
Project description:Physiological and gene expression studies of deep-sea bacteria under pressure conditions similar to those experienced in their natural habitat are critical to understand growth kinetics and metabolic adaptations to in situ conditions. The Epslilonproteobacterium, Nautilia sp. strain PV1, was isolated from hydrothermal fluids released from an active deep-sea hydrothermal vent at 9°N on the East Pacific Rise. Using a high pressure/high temperature continuous culture system we established that strain PV-1 has the shortest generation time of all known piezophilic microorganisms and we investigated its protein expression pattern in response to different hydrostatic pressures. Proteomic analyses of strain PV-1 grown at 200 Bars and 5 Bars showed that pressure adaptation is not restricted only to stress response or homeoviscous adaptation, but that it is more diversified and protein specific, with a fine and variegated regulation of enzymes involved even in the same metabolic pathway. As previously reported, proteins synthesis, motility, transport and energy metabolism are all affected by pressure, although to different extents. In strain PV-1, low pressure condition seems to activate the synthesis of phage-related proteins and an overexpression of enzymes involved in central carbon metabolism.
Project description:Environmental extracts and fractions obtained with passive sampling (HP-20, SMIRC) from Mission Bay, Point Loma, Scripps Pier, Salton Sea (San Diego and Imperial Counties)
Project description:The sea cucumber Apostichopus japonicus withstands high water temperatures in the summer by suppressing metabolic rate and entering a state of aestivation. We hypothesized that changes in the expression of miRNAs could provide important post-transcriptional regulation of gene expression during hypometabolism via control over mRNA translation. The present study analyzed profiles of miRNA expression in the sea cucumber respiratory tree using Solexa deep sequencing technology. We identified 279 sea cucumber miRNAs, including 15 novel miRNAs specific to sea cucumber. Animals sampled during deep aestivation (DA; after at least 15 days of continuous torpor) were compared with animals from a non-aestivation (NA) state (animals that had passed through aestivation and returned to an active state). We identified 30 differentially expressed miRNAs ([RPM (reads per million) >10, |FC| (|fold change|) M-bM-^IM-%1, FDR (false discovery rate) <0.01]) during aestivation, which were validated by two other miRNA profiling methods: miRNA microarray and real-time PCR. Among the most prominent miRNA species, miR-124, miR-124-3p, miR-79, miR-9 and miR-2010 were significantly over-expressed during deep aestivation compared with non-aestivation animals, suggesting that these miRNAs may play important roles in metabolic rate suppression during aestivation. In the present study, an analysis of the global profile of small RNAs was conducted using Solexa sequencing technology in non-aestivation (NA) and deep aestivation (DA) sea cucumbers. We focus on respiratory tree in the present study because it is the important site responsible for the strong metabolic rate depression seen under deep aestivating conditions and the global expression profile of mRNA from the this organ has also been constructed applying RNA-seq technology in our previous study (Zhao and Chen, unpublished data). A preliminary analysis of the functional relevance of miRNA expression in relation to hypometabolism during aestivation is presented. A miRNA microarray and RT-qPCR were both used to supplement and confirm differentially expressed miRNAs. Our findings provide important new insights into the molecular mechanisms of sea cucumber aestivation.