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The deep ocean is the largest biome on Earth and yet it is among the least studied environments of our planet. Life at great depths requires several specific adaptations; however, their molecular mechanisms remain understudied. We examined patterns of positive selection in 416 genes from four brittle star (Ophiuroidea) families displaying replicated events of deep-sea colonization (288 individuals from 216 species). We found consistent signatures of molecular convergence in functions related to protein biogenesis, including protein folding and translation. Five genes were recurrently positively selected, including chaperonin-containing TCP-1 subunit α (CCTα), which is essential for protein folding. Molecular convergence was detected at the functional and gene levels but not at the amino-acid level. Pressure-adapted proteins are expected to display higher stability to counteract the effects of denaturation. We thus examined in silico local protein stability of CCTα across the ophiuroid tree of life (967 individuals from 725 species) in a phylogenetically corrected context and found that deep-sea-adapted proteins display higher stability within and next to the substrate-binding region, which was confirmed by in silico global protein stability analyses. This suggests that CCTα displays not only structural but also functional adaptations to deep-water conditions. The CCT complex is involved in the folding of ∼10% of newly synthesized proteins and has previously been categorized as a "cold-shock" protein in numerous eukaryotes. We thus propose that adaptation mechanisms to cold and deep-sea environments may be linked and highlight that efficient protein biogenesis, including protein folding and translation, is a key metabolic deep-sea adaptation. [ABSTRACT FROM AUTHOR]

Advancement in marine robotics adaptability, which is crucial for efficient task completion in complex marine environments, is the central focus of contemporary research. This paper discusses the ongoing research and future prospects of environmentally adaptable marine robots. Initially, we provide an overview of how marine robots adapt to varying seawater pressure and buoyancy at different depths. Following this, pressure and buoyancy adaptation technologies are elaborated upon and critically analysed. The shortcomings of conventional rigid pressure resistance are addressed, along with potential solutions using pressure compensation and flexible pressure-resistance methods. Furthermore, we examine the limitations of traditional active buoyancy control and, propose improvements through passive buoyancy and an active-passive cooperative control strategy. Noteworthy advancements including active buoyancy control based on phase-change principle and fully-passive buoyancy control based on fluid compression are identified as promising areas for future development. Lastly, we outline the challenges and prospective directions for the development of adaptive technologies for marine robots, including soft-body and bionic designs, novel material applications, and innovative control methods for marine robots. This study is expected to serve as a valuable reference for future research into deep-sea marine robotic technologies. • A review of the existing research into environment adaptation in marine robots is presented. • Pressure resistance (rigid, flexible, compensation) and buoyancy (active, passive, active-passive cooperative) adaptation technologies are discussed. • Several promising areas for future development are proposed. • Outstanding problems and future prospects in bio-hybrids, soft-bodied robots, and novel materials for environmental adaptability are given. [ABSTRACT FROM AUTHOR]

The deep biosphere is often characterized by multiple extreme physical–chemical conditions, of which pressure is an important parameter that influences life but remains less studied. This geomicrobiology study was designed to understand the response of a subterranean microbial community of the Deccan traps to high-pressure conditions and to elucidate their genomic properties. Groundwater from a deep basaltic aquifer of the Deccan traps was used to ascertain the community response to 25 MPa and 50 MPa pressure following enrichment in high-salt and low-salt organic media. Quantitative PCR data indicated a decrease in bacterial and archaeal cell numbers with increasing pressure. 16S rRNA gene sequencing displayed substantial changes in the microbial community in which Acidovorax appeared to be the most dominant genus in the low-salt medium and Microbacteriaceae emerged as the major family in the high-salt medium under both pressure conditions. Genes present in metagenome-associated genomes which have previously been associated with piezotolerance include those related to nutrient uptake and extracytoplasmic stress (omp, rseC), protein folding and unfolding (dnaK, groEL and others), and DNA repair mechanisms (mutT, uvr and others). We hypothesize that these genes facilitate tolerance to high pressure by certain groups of microbes residing in subsurface Deccan traps. [ABSTRACT FROM AUTHOR]

New phagotrophic euglenoid species from marine surface waters and the deep sea were isolated and described by light and scanning electron microscopy and 18S rDNA sequencing: Keelungia nitschei , Petalomonas acorensis and Ploeotia costaversata. The morphological characteristics of Keelungia nitschei agree with Keelungia pulex besides the slightly truncated anterior front of the cell of our strain. Phylogenetic analysis indicated low sequence similarity between K. nitschei and K. pulex (87.3%). Ploeotia costaversata clustered within the Ploeotia costata clade with a sequence similarity of 96.1% to P. costata strain Tam. Ultrastructural characteristics of our strain revealed helically twisted strips towards both poles of the protoplast. 18S rDNA phylogenies showed that Petalomonas acorensis is related to the clade of Petalomonas cantuscygni/Scytomonas saepesedens with the highest sequence similarity of 81.2% to P. cantuscygni. Six pellicle strips are visible, while two of them reach only the middle of the cell and four (two longitudinal, two helically twisted) join at the posterior front of the cell. Pressure experiments showed that the deep-sea strain K. nitschei was better adapted to high hydrostatic pressures (up to 500 bar) at 4 °C than the two surface water strains. All three strains increased the database (18S rDNA) of the underrepresented group of phagotrophic euglenids. [ABSTRACT FROM AUTHOR]

Abstract The discovery of microbial communities in extreme conditions that would seem hostile to life leads to the question of how the molecules making up these microbes can maintain their structure and function. While microbes that live under extremes of temperature have been heavily studied, those that live under extremes of pressure, or "piezophiles", are now increasingly being studied because of advances in sample collection and high-pressure cells for biochemical and biophysical measurements. Here, adaptations of enzymes in piezophiles against the effects of pressure are discussed in light of recent experimental and computational studies. However, while concepts from studies of enzymes from temperature extremophiles can provide frameworks for understanding adaptations by piezophile enzymes, the effects of temperature and pressure on proteins differ in significant ways. Thus, the state of the knowledge of adaptation in piezophile enzymes is still in its infancy and many more experiments and computational studies on different enzymes from a variety of piezophiles are needed. [ABSTRACT FROM AUTHOR]

Isolations of pressure-adapted deep sea bacteria from depths of 1,400 to 5,100 m resulted in a variety of psychrophilic barotolerant and barophilic strains. Growth rates determined at different pressures indicated a gradual transition between the two types of pressure-adapted isolates. The presence of barotolerant bacteria in deep water, sustained by sinking particulate matter, causes the nonbarophilic response of natural populations, i.e., increased growth after decompression. With increasing pressure-adaptation in barophilic isolates the maximum growth rates at optimum pressures decrease. Thus, the observed general slow-down of microbial activity in the deep sea takes effect regardless of the common occurrence of psychrophilic and barophilic bacteria. The highest degree of barophilism was observed in isolates from nutrient-rich habitats such as intestinal tracts of deep sea animals or decaying carcasses. Detailed studies with an isolate, growing barophilically on a complex as well as a single-carbon-source medium, showed that (1) culturing at pressures lower than optimal for growth resulted in the formation of cell filaments, (2) growth was unaffected by repeated compression/decompression cycles and (3) no perceptible differences in the distribution of radiolabeled carbon from an amino acid mixture occurred in cells grown at, below and above the pressure optimal for growth. [ABSTRACT FROM AUTHOR]