Sea ice is one of the most frigid environments for marine microbes. In contrast to other ocean ecosystems, microbes in permanent sea ice are space confined and subject to many extreme conditions, which change on a seasonal basis. How these microbial communities are regulated to survive the extreme sea ice environment is largely unknown. Here, we show that filamentous phages regulate the host bacterial community to improve survival of the host in permanent Arctic sea ice. We isolated a filamentous phage, f327, from an Arctic sea ice Pseudoalteromonas strain, and we demonstrated that this type of phage is widely distributed in Arctic sea ice. Growth experiments and transcriptome analysis indicated that this phage decreases the host growth rate, cell density and tolerance to NaCl and H2O2, but enhances its motility and chemotaxis. Our results suggest that the presence of the filamentous phage may be beneficial for survival of the host community in sea ice in winter, which is characterized by polar night, nutrient deficiency and high salinity, and that the filamentous phage may help avoid over blooming of the host in sea ice in summer, which is characterized by polar day, rich nutrient availability, intense radiation and high concentration of H2O2. Thus, while they cannot kill the host cells by lysing them, filamentous phages confer properties advantageous to host survival in the Arctic sea ice environment. Our study provides a foremost insight into the ecological role of filamentous phages in the Arctic sea ice ecosystem.
The structure and function of an enzyme can be altered by nanoparticles (NPs). The interaction between enzyme and NPs is governed by the key properties of NPs, such as structure, size, surface chemistry, charge and surface shape. Recent representative studies on the NP-enzyme interactions and the regulation of enzyme activity by NPs with different size, composition and surface modification are reviewed.
Background Diabetic limb ischemia is a clinical syndrome and refractory to therapy. Our previous study demonstrated that adipose-derived stem cells (ADSCs) overexpressing glyoxalase-1 (GLO-1) promoted the regeneration of ischemic lower limbs in diabetic mice, but low survival rate, difficulty in differentiation, and tumorigenicity of the transplanted cells restricted its application. Recent studies have found that exosomes secreted by the ADSCs have the advantages of containing parental beneficial factors and exhibiting non-immunogenic, non-tumorigenic, and strong stable characteristics. Methods ADSCs overexpressing GLO-1 (G-ADSCs) were established using lentivirus transfection, and exosomes secreted from ADSCs (G-ADSC-Exos) were isolated and characterized to coculture with human umbilical vein endothelial cells (HUVECs). Proliferation, apoptosis, migration, and tube formation of the HUVECs were detected under high-glucose conditions. The G-ADSC-Exos were injected into ischemic hindlimb muscles of type 2 diabetes mellitus (T2DM) mice, and the laser Doppler perfusion index, Masson’s staining, immunofluorescence, and immunohistochemistry assays were adopted to assess the treatment efficiency. Moreover, the underlying regulatory mechanisms of the G-ADSC-Exos on the proliferation, migration, angiogenesis, and apoptosis of the HUVECs were explored. Results The G-ADSC-Exos enhanced the proliferation, migration, tube formation, and anti-apoptosis of the HUVECs in vitro under high-glucose conditions. After in vivo transplantation, the G-ADSC-Exo group showed significantly higher laser Doppler perfusion index, better muscle structural integrity, and higher microvessel’s density than the ADSC-Exo and control groups by Masson’s staining and immunofluorescence assays. The underlying mechanisms by which the G-ADSC-Exos protected endothelial cells both in vitro and in vivo might be via the activation of eNOS/AKT/ERK/P-38 signaling pathways, inhibition of AP-1/ROS/NLRP3/ASC/Caspase-1/IL-1β, as well as the increased secretion of VEGF, IGF-1, and FGF. Conclusion Exosomes derived from adipose-derived stem cells overexpressing GLO-1 protected the endothelial cells and promoted the angiogenesis in type 2 diabetic mice with limb ischemia, which will be a promising clinical treatment in diabetic lower limb ischemia.
BackgroundPseudoalteromonas is an important genus widespread in marine environment, and a lot of psychrophilic Pseudoalteromonas strains thrive in deep sea and polar sea. By now, there are only a few genetic systems for Pseudoalteromonas reported and no commercial Pseudoalteromonas genetic system is available, which impedes the study of Pseudoalteromonas, especially for psychrophilic strains. The aim of this study is to develop a heterologous expression system for psychrophilic Pseudoalteromonas.ResultsA cryptic plasmid pSM429 isolated from psychrophilic Pseudoalteromonas sp. BSi20429 from the Arctic sea ice, was sequenced and characterized. The plasmid pSM429 is 3874 bp in length, with a G+C content of 28%. Four putative open reading frames (ORFs) were identified on pSM429. Based on homology, the ORF4 was predicted to encode a replication initiation (Rep) protein. A shuttle vector (Escherichia coli, Pseudoalteromonas), pWD, was constructed by ligating pSM429 and pUC19 and inserting a chloramphenicol acetyl transferase (CAT) cassette conferring chloramphenicol resistance. To determine the minimal replicon of pSM429 and to check the functionality of identified ORFs, various pWD derivatives were constructed. All derivatives except the two smallest ones were shown to allow replication in Pseudoalteromonas sp. SM20429, a plasmid-cured strain of Pseudoalteromonas sp. BSi20429, suggesting that the orf4 and its flanking intergenic regions are essential for plasmid replication. Although not essential, the sequence including some repeats between orf1 and orf2 plays important roles in segregational stability of the plasmid. With the aid of pWD-derived plasmid pWD2, the erythromycin resistance gene and the cd gene encoding the catalytic domain of a cold-adapted cellulase were successfully expressed in Pseudoalteromonas sp. SM20429.ConclusionsPlasmid pSM429 was isolated and characterized, and the regions essential for plasmid replication and stability were determined, helping the development of pSM429-based shuttle vectors. The shuttle vectors pWD and its derivatives could be used as cloning vectors for Pseudoalteromonas, offering new perspectives in the genetic manipulation of Pseudoalteromonas strains. With the aid of pWD-derived vector and its host, the erythromycin resistance gene and the cd gene of a cold-adapted protein were successfully expressed, indicating that the potential use of this system for recombinant protein production, especially for cold-adapted proteins.
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