Mechanistic Insight into the Fragmentation of Type I Collagen Fibers into Peptides and Amino Acids by a Vibrio Collagenase.

Vibrio collagenases of the M9A subfamily are closely related to Vibrio pathogenesis for their role in collagen degradation during host invasion. Although some Vibrio collagenases have been characterized, the collagen degradation mechanism of Vibrio collagenase is still largely unknown. Here, an M9A collagenase, VP397, from marine Vibrio pomeroyi strain 12613 was characterized, and its fragmentation pattern on insoluble type I collagen fibers was studied. VP397 is a typical Vibrio collagenase composed of a catalytic module featuring a peptidase M9N domain and a peptidase M9 domain and two accessory bacterial prepeptidase C-terminal domains (PPC domains). It can hydrolyze various collagenous substrates, including fish collagen, mammalian collagens of types I to V, triple-helical peptide [(POG)10]3, gelatin, and 4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-o-Arg (Pz-peptide). Atomic force microscopy (AFM) observation and biochemical analyses revealed that VP397 first assaults the C-telopeptide region to dismantle the compact structure of collagen and dissociate tropocollagen fragments, which are further digested into peptides and amino acids by VP397 mainly at the Y-Gly bonds in the repeating Gly-X-Y triplets. In addition, domain deletion mutagenesis showed that the catalytic module of VP397 alone is capable of hydrolyzing type I collagen fibers and that its C-terminal PPC2 domain functions as a collagen-binding domain during collagenolysis. Based on our results, a model for the collagenolytic mechanism of VP397 is proposed. This study sheds light on the mechanism of collagen degradation by Vibrio collagenase, offering a better understanding of the pathogenesis of Vibrio and helping in developing the potential applications of Vibrio collagenase in industrial and medical areas. IMPORTANCE Many Vibrio species are pathogens and cause serious diseases in humans and aquatic animals. The collagenases produced by pathogenic Vibrio species have been regarded as important virulence factors, which occasionally exhibit direct pathogenicity to the infected host or facilitate other toxins' diffusion through the digestion of host collagen. However, our knowledge concerning the collagen degradation mechanism of Vibrio collagenase is still limited. This study reveals the degradation strategy of Vibrio collagenase VP397 on type I collagen. VP397 binds on collagen fibrils via its C-terminal PPC2 domain, and its catalytic module first assaults the C-telopeptide region and then attacks the Y-Gly bonds in the dissociated tropocollagen fragments to release peptides and amino acids. This study offers new knowledge regarding the collagenolytic mechanism of Vibrio collagenase, which is helpful for better understanding the role of collagenase in Vibrio pathogenesis and for developing its industrial and medical applications.

Structure of Vibrio collagenase VhaC provides insight into the mechanism of bacterial collagenolysis.

The collagenases of Vibrio species, many of which are pathogens, have been regarded as an important virulence factor. However, there is little information on the structure and collagenolytic mechanism of Vibrio collagenase. Here, we report the crystal structure of the collagenase module (CM) of Vibrio collagenase VhaC and the conformation of VhaC in solution. Structural and biochemical analyses and molecular dynamics studies reveal that triple-helical collagen is initially recognized by the activator domain, followed by subsequent cleavage by the peptidase domain along with the closing movement of CM. This is different from the peptidolytic mode or the proposed collagenolysis of Clostridium collagenase. We propose a model for the integrated collagenolytic mechanism of VhaC, integrating the functions of VhaC accessory domains and its collagen degradation pattern. This study provides insight into the mechanism of bacterial collagenolysis and helps in structure-based drug design targeting of the Vibrio collagenase.

Marinifaba aquimaris gen. nov., sp. nov., a novel chitin-degrading gammaproteobacterium in the family Alteromonadaceae isolated from seawater of the Mariana Trench.

A novel Gram-negative, rod-shaped, aerobic, oxidase-positive and catalase-negative bacterium, designated strain SM1970T, was isolated from a seawater sample collected from the Mariana Trench. Strain SM1970T grew at 15-37 oC and with 1-5% (w/v) NaCl. It hydrolyzed colloidal chitin, agar and casein but did not reduce nitrate to nitrite. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain SM1970T formed a distinct lineage close to the genus Catenovulum within the family Alteromonadaceae, sharing the highest sequence similarity (93.6%) with type strain of Catenovulum maritimum but < 93.0% sequence similarity with those of other known species in the class Gammaproteobacteria. The major fatty acids of strain SM1970T were summed feature 3 (C16: 1 ω7c and/or C16: 1 ω6c), C16: 0 and summed feature 8 (C18: 1 ω7c and/or C18: 1 ω6c). The major polar lipids of the strain included phosphatidylethanolamine and phosphatidylglycerol and its main respiratory quinone was ubiquinone 8. The draft genome of strain SM1970T consisted of 77 scaffolds and was 4,172,146 bp in length, containing a complete set of genes for chitin degradation. The average amino acid identity (AAI) values between SM1970T and type strains of known Catenovulum species were 56.6-57.1% while the percentage of conserved proteins (POCP) values between them were 28.5-31.5%. The genomic DNA G + C content of strain SM1970T was 40.1 mol%. On the basis of the polyphasic analysis, strain SM1970T is considered to represent a novel species in a novel genus of the family Alteromonadaceae, for which the name Marinifaba aquimaris is proposed with the type strain being SM1970T (= MCCC 1K04323T = KCTC 72844T).

Marinomonas profundi sp. nov., isolated from deep seawater of the Mariana Trench.

A Gram-stain-negative, aerobic, polarly flagellated, straight or curved rod-shaped bacterium, designated strain M1K-6T, was isolated from deep seawater samples collected from the Mariana Trench. The strain grew at -4 to 37 °C (optimum, 25-30 °C), at pH 5.5-10.0 (optimum, pH 7.0) and with 0.5-14.0  % (w/v) NaCl (optimum, 2.0 %). It did not reduce nitrate to nitrite nor hydrolyse gelatin or starch. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain M1K-6T was affiliated with the genus Marinomonas, sharing 93.1-97.0  % sequence similarity with the type strains of recognized Marinomonas species. The major cellular fatty acids were summed feature 3 (C16 : 1 ω6c/C16 : 1 ω7c), summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C16 : 0, C10 : 0 3-OH and C18 : 0. The predominant respiratory quinone was ubiquinone-8. Polar lipids of strain M1K-6T included phosphatidylethanolamine, phosphatidylglycerol and two unidentified lipids. The genomic G+C content of strain M1K-6T was 46.0 mol%. Based on data from the present polyphasic study, strain M1K-6T was considered to represent a novel species within the genus Marinomonas, for which the name Marinomonas profundi sp. nov. is proposed. The type strain is M1K-6T (=KCTC 72501T=MCCC 1K03890T).

3,6-Anhydro-L-Galactose Dehydrogenase VvAHGD is a Member of a New Aldehyde Dehydrogenase Family and Catalyzes by a Novel Mechanism with Conformational Switch of Two Catalytic Residues Cysteine 282 and Glutamate 248.

3,6-anhydro-α-L-galactose (L-AHG) is one of the main monosaccharide constituents of red macroalgae. In the recently discovered bacterial L-AHG catabolic pathway, L-AHG is first oxidized by a NAD(P)+-dependent dehydrogenase (AHGD), which is a key step of this pathway. However, the catalytic mechanism(s) of AHGDs is still unclear. Here, we identified and characterized an AHGD from marine bacterium Vibrio variabilis JCM 19239 (VvAHGD). The NADP+-dependent VvAHGD could efficiently oxidize L-AHG. Phylogenetic analysis suggested that VvAHGD and its homologs represent a new aldehyde dehydrogenase (ALDH) family with different substrate preferences from reported ALDH families, named the L-AHGDH family. To explain the catalytic mechanism of VvAHGD, we solved the structures of VvAHGD in the apo form and complex with NADP+ and modeled its structure with L-AHG. Based on structural, mutational, and biochemical analyses, the cofactor channel and the substrate channel of VvAHGD are identified, and the key residues involved in the binding of NADP+ and L-AHG and the catalysis are revealed. VvAHGD performs catalysis by controlling the consecutive connection and interruption of the cofactor channel and the substrate channel via the conformational changes of its two catalytic residues Cys282 and Glu248. Comparative analyses of structures and enzyme kinetics revealed that differences in the substrate channels (in shape, size, electrostatic surface, and residue composition) lead to the different substrate preferences of VvAHGD from other ALDHs. This study on VvAHGD sheds light on the diversified catalytic mechanisms and evolution of NAD(P)+-dependent ALDHs.

Shewanella polaris sp. nov., a psychrotolerant bacterium isolated from Arctic brown algae.

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901T, was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901T was affiliated with the genus Shewanella, showing the highest sequence similarity to the type strain of Shewanella litoralis (97.5%), followed by those of Shewanella vesiculosa, Shewanella livingstonensis and Shewanella saliphila (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C16 : 1 ω7с and/or C16 : 1 ω6с), C16 : 0, C18 : 0, iso-C15 : 0 and C17 : 1 ω8с and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar Shewanella species, within the genus Shewanella, for which the name Shewanella polaris sp. nov. is proposed. The type strain is SM1901T (=KCTC 72047T=MCCC 1K03585T).

Parvularcula marina sp. nov., isolated from surface water of the South China Sea, and emended description of the genus Parvularcula.

A Gram-stain-negative, aerobic, flagellated, rod-shaped bacterial strain, SM1705T, was isolated from a surface seawater sample collected from the South China Sea. The strain grew at 10-40 °C and with 0.5-13.0 % (w/v) NaCl. It hydrolysed Tweens 20, 40 and 60, but did not hydrolyse starch or Tween 80 nor reduce nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1705T was affiliated with the genus Parvularcula, sharing the highest sequence similarity (96.0 %) with type strain of Parvularcula bermudensis and forming a coherent branch together with the latter within the clade of Parvularcula. The major cellular fatty acids were identified as summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), C16 : 0 and C18 : 0. Polar lipids included three unidentified glycolipids and one unidentified lipid. The major respiratory quinone of strain SM1705T was Q10. The genomic DNA G+C content of strain SM1705T was 59.3 mol%. Based on the polyphasic evidence presented in this paper, strain SM1705T represents a novel Parvularcula species, for which the name Parvularcula marina sp. nov. is proposed. The type strain is SM1705T (=KCTC 62795T=MCCC 1K03505T=CCTCC AB 2018345T).

Phycobiliproteins: Molecular structure, production, applications, and prospects.

Phycobiliproteins (PBPs) are the main component of light-harvesting complexes in cyanobacteria and red algae. In addition to their important role in photosynthesis, PBPs have many potential applications in foods, cosmetics, medical diagnosis and treatment of diseases. However, basic researches and technological innovations are urgently needed for exploring those potentials, such as structure and function, their biosynthesis as well as downstream purification. For medical use and application, mechanisms underlying their therapeutic effects must be elucidated. Focusing on these issues, this article gives a critical review on the current status on PBPs, including their structures and functions, preparation processes and applications. In addition, key technical challenges and possible solutions are prospected.

Flavobacterium arcticum sp. nov., isolated from Arctic seawater.

A Gram-reaction-negative, aerobic, non-flagellated, rod-shaped and yellow-pigmented bacterium, designated strain SM1502T, was isolated from Arctic seawater. The isolate grew at 10-40 °C and with 0-8.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate was affiliated with the genus Flavobacterium, with the highest sequence similarity (96.0 %) found with Flavobacterium suzhouense XIN-1T. The major fatty acids of strain SM1502T were iso-C15 : 0, iso-C17 : 1ω9c, iso-C15 : 1 G, C15 : 0, iso-C17 : 0 3-OH and unknown ECL 13.565. The major respiratory quinone of strain SM1502T was menaquinone-6 (MK-6). Polar lipids of strain SM1502T included phosphatidylethanolamine and one unidentified aminolipid and lipid. The genomic DNA G+C content of strain SM1502T was 37.0 mol%. Based on the polyphasic data obtained in this study, strain SM1502T is considered to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium arcticum sp. nov. is proposed. The type strain is SM1502T (=KCTC 42668T=CCTCC AB 2015346T).

Subsaxibacter arcticus sp. nov., isolated from Arctic intertidal sand.

A Gram-negative, orange-pigmented, aerobic, non-flagellated, rod-shaped bacterium, designated strain SM1214T, was isolated from Arctic intertidal sand collected from Kongsfjorden, Svalbard. The strain grew at 10-30 °C and with 0.5-5 % (w/v) NaCl. It hydrolysed casein and aesculin but did not reduce nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1214T was affiliated with the genus Subsaxibacter in the family Flavobacteriaceae, exhibiting 96.7 % 16S rRNA gene sequence similarity to the type strain of Subsaxibacter broadyi, the only recognized species of the genus. The major cellular fatty acids of strain SM1214T were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G, C15 : 0, summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), anteiso-C15 : 0 and C17 : 0 2-OH. The genomic DNA G+C content of the strain was 35.4 mol%. On the basis of the polyphasic analysis performed in this study, strain SM1214T represents a novel species of the genus Subsaxibacter, for which the name Subsaxibacter arcticus sp. nov. is proposed. The type strain is SM1214T ( = JCM 30334T = CCTCC AB 2014245T).

Arcticiflavibacter luteus gen. nov., sp. nov., a member of the family Flavobacteriaceae isolated from intertidal sand.

A yellow-pigmented, rod-shaped, non-flagellated, aerobic and Gram-reaction-negative bacterium, designated strain SM1212T, was isolated from intertidal sand of Kongsfjorden, Svalbard. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1212T constituted a distinct lineage within the family Flavobacteriaceae. It shared highest 16S rRNA gene sequence similarities with the type strains of Bizionia echini (96.0 %), Lacinutrix jangbogonensis (95.8 %) and Psychroserpens damuponensis (95.7 %) and < 95.6 % sequence similarity with other recognized species in the family Flavobacteriaceae. The strain grew at 4-35 °C and with 0-6.0 % (w/v) NaCl. It hydrolysed gelatin, DNA, starch and Tween 80 but did not reduce nitrate to nitrite. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, iso-C15 : 1 G, anteiso-C15 : 1 A, iso-C15 : 0 3-OH, C17 : 0 2-OH and iso-C17 : 0 3-OH and the major respiratory quinone was menaquinone MK-6. Polar lipids included phosphatidylethanolamine, one unidentified phospholipid, one unidentified aminophospholipid, three unidentified aminolipids and nine unidentified lipids. The genomic DNA G+C content of strain SM1212T was 36.6 mol%. On the basis of data from this polyphasic study, strain SM1212T represents a novel species in a new genus in the family Flavobacteriaceae, for which the name Arcticiflavibacter luteus gen. nov., sp. nov. is proposed. The type strain of Arcticiflavibacter luteus is SM1212T ( = MCCC 1K00234T = KCTC 32514T).

Algimonas arctica sp. nov., isolated from intertidal sand, and emended description of the genus Algimonas.

A novel Gram-reaction-negative, aerobic, pale-orange-pigmented bacterium, designated strain SM1216T, was isolated from Arctic intertidal sand. Cells of strain SM1216T were dimorphic rods with a single polar prostheca or flagellum. The strain grew at 4 − 30 °C (optimum at 25 °C) and with 0.5 − 6 % (w/v) NaCl (optimum with 2 − 3 %). It reduced nitrate to nitrite but did not hydrolyse gelatin, DNA or Tween 80. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1216T was affiliated with the genus Algimonas in the family Hyphomonadaceae, sharing 97.5 and 96.3 % similarity with Algimonas ampicilliniresistens 14A-2-7T and Algimonas porphyrae 0C-2-2T, respectively, the two known species in the genus Algimonas. However, the level of DNA­DNA relatedness between strain SM1216T and the type strain of A. ampicilliniresistens, the nearest phylogenetic neighbour, was 57.9 %. The major cellular fatty acids of strain SM1216T were C18 : 1ω7c and C18 : 1 2-OH. The main polar lipids of strain SM1216T were monoglycosyldiglyceride (MGDG), glucuronopyranosyldiglyceride (GUDG), phosphatidylglycerol (PG) and three unidentified phospholipids (PL1­3). The major respiratory quinone was ubiquinone 10 (Q10). The genomic G+C content of strain SM1216T was 60.6 mol%. On the basis of the evidence from this polyphasic study, strain SM1216T represents a novel species in the genus Algimonas, for which the name Algimonas arctica sp. nov. is proposed. The type strain is SM1216T ( = MCCC 1K00233T = KCTC 32513T). An emended description of the genus Algimonas is also given.

Haliea atlantica sp. nov., isolated from seawater, transfer of Haliea mediterranea to Parahaliea gen. nov. as Parahaliea mediterranea comb. nov. and emended description of the genus Haliea.

A novel Gram-stain-negative, oxidase- and catalase-positive, aerobic bacterium, designated strain SM1351T, was isolated from surface seawater of the Atlantic Ocean. This strain grew at 4-45 °C and with 5-90 g NaCl l- 1. It did not reduce nitrate to nitrite and could not hydrolyse starch or DNA. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain was affiliated with the genus Haliea in the family Alteromonadaceae, with sequence similarities with the type strains of Haliea salexigens and Haliea mediterranea, the two recognized species of the genus Haliea, of 96.2 and 94.6 %, respectively. The major fatty acids of strain SM1351T were C16 : 1ω7c and/or iso-C15 : 0 2-OH, C17 : 1ω8c, C18 : 1ω7c and C16 : 0 and the major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The major respiratory quinone was ubiquinone Q-8. The genomic DNA G+C content of strain SM1351T was 62 mol%. On the basis of the polyphasic characterization of strain SM1351T in this study, it is considered to represent a novel species in the genus Haliea, for which the name Haliea atlantica sp. nov. is proposed. The type strain is SM1351T ( = CCTCC AB 2014266T = JCM 30304T). Moreover, the transfer of Haliea mediterraneaLucena et al. 2010 to Parahaliea gen. nov. as Parahaliea mediterranea comb. nov. (type strain 7SM29T = CECT 7447T = DSM 21924T) and an emended description of the genus Haliea are also proposed.

Bizionia arctica sp. nov., isolated from Arctic fjord seawater, and emended description of the genus Bizionia.

A Gram-stain-negative, yellow-pigmented, aerobic, non-flagellated, non-gliding bacterial strain, designated SM1203(T), was isolated from surface seawater of Kongsfjorden, Svalbard. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1203(T) was affiliated with the genus Bizionia in the family Flavobacteriaceae. The strain shared the highest 16S rRNA gene sequence similarity (>96%) with the type strains of Formosa spongicola (96.8%), Bizionia paragorgiae (96.3%), B. saleffrena (96.3%) and B. echini (96.1%) and 95.4-95.7% sequence similarity with the type strains of other known species of the genus Bizionia. The strain grew at 4-30 °C and in the presence of 1.0-5.0% (w/v) NaCl. The major fatty acids of strain SM1203(T) were iso-C15 : 0, iso-C15 : 1, anteiso-C15 : 0 and C15 : 0 and the main polar lipids were phosphatidylethanolamine and an unidentified lipid. The major respiratory quinone of strain SM1203(T) was menaquinone 6 (MK-6). The genomic DNA G+C content of strain SM1203(T) was 34.8 mol%. Based on the polyphasic characterization of strain SM1203(T) in this study, the strain represents a novel species in the genus Bizionia, for which the name Bizionia arctica sp. nov. is proposed. The type strain is SM1203(T) ( = CGMCC 1.12751(T) = JCM 30333(T)). An emended description of the genus Bizionia is also given.

Marivirga atlantica sp. nov., isolated from seawater and emended description of the genus Marivirga.

A novel Gram-stain-negative, aerobic, orange-pigmented, non-flagellated, gliding, rod-shaped bacterium, designated strain SM1354(T) was isolated from surface seawater of the Atlantic Ocean. The strain hydrolysed gelatin and DNA but did not reduce nitrate. It grew at 4-40 °C and with 0.5-11% (w/v) NaCl. Phylogenetic analysis of the 16S rRNA gene sequences revealed that strain SM1354(T) belonged to the genus Marivirga with 96.0-96.2% sequence similarities to known species of the genus Marivirga . The major fatty acids of strain SM1354(T) were iso-C15 : 0, iso-C15 : 1 G, iso-C17 : 03-OH and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 02-OH). Polar lipids of strain SM1354(T) included phosphatidylethanolamine, three unidentified lipids and one unidentified aminolipid and aminophospholipid. The major respiratory quinone of strain SM1354(T) was menaquinone 7 (MK-7). The genomic DNA G+C content of strain SM1354(T) was 33.9 ± 0.4 mol%. On the basis of the results of the polyphasic characterization in this study, it is proposed that strain SM1354(T) represents a novel species of the genus Marivirga , namely Marivirga atlantica sp. nov. The type strain of Marivirga atlantica is SM1354(T) ( =CCTCC AB 2014242(T) =JCM 30305(T)). An emended description of the genus Marivirga is also proposed.

Antimicrobial peptide trichokonin VI-induced alterations in the morphological and nanomechanical properties of Bacillus subtilis.

Antimicrobial peptides are promising alternative antimicrobial agents compared to conventional antibiotics. Understanding the mode of action is important for their further application. We examined the interaction between trichokonin VI, a peptaibol isolated from Trichoderma pseudokoningii, and Bacillus subtilis, a representative Gram-positive bacterium. Trichokonin VI was effective against B. subtilis with a minimal inhibitory concentration of 25 µM. Trichokonin VI exhibited a concentration- and time-dependent effect against B. subtilis, which was studied using atomic force microscopy. The cell wall of B. subtilis collapsed and the roughness increased upon treatment with trichokonin VI. Nanoindentation experiments revealed a progressive decrease in the stiffness of the cells. Furthermore, the membrane permeabilization effect of trichokonin VI on B. subtilis was monitored, and the results suggest that the leakage of intracellular materials is a possible mechanism of action for trichokonin VI, which led to alterations in the morphological and nanomechanical properties of B. subtilis.

Mechanical manipulation assisted self-assembly to achieve defect repair and guided epitaxial growth of individual peptide nanofilaments.

We have succeeded in the production of defect-free and spatially organized individual one-dimensional peptide nanofilaments by real-time control of the self-assembly process on a solid substrate. Using a unique mechanical manipulation method based on atomic force microscopy, we are able to introduce mechanical stimuli to generate active ends at designated positions on an existing peptide nanofilament previously formed. By doing so, defects in the filament were removed, and self-repairing occurred when the active ends extended along the direction of the supporting lattice, resulting in the closure of the broken filament. Furthermore, new active ends of the nanofilaments can be specifically generated to guide the self-assembly of new filaments at designated positions with selected orientations. The mechanism of defect repair and guided epitaxial growth is also discussed.

The supramolecular architecture, function, and regulation of thylakoid membranes in red algae: an overview.

Red algae are a group of eukaryotic photosynthetic organisms. Phycobilisomes (PBSs), which are composed of various types of phycobiliproteins and linker polypeptides, are the main light-harvesting antennae in red algae, as in cyanobacteria. Two morphological types of PBSs, hemispherical- and hemidiscoidal-shaped, are found in different red algae species. PBSs harvest solar energy and efficiently transfer it to photosystem II (PS II) and finally to photosystem I (PS I). The PS I of red algae uses light-harvesting complex of PS I (LHC I) as a light-harvesting antennae, which is phylogenetically related to the LHC I found in higher plants. PBSs, PS II, and PS I are all distributed throughout the entire thylakoid membrane, a pattern that is different from the one found in higher plants. Photosynthesis processes, especially those of the light reactions, are carried out by the supramolecular complexes located in/on the thylakoid membranes. Here, the supramolecular architecture, function and regulation of thylakoid membranes in red algal are reviewed.