Paraglaciecola hydrolytica sp. nov., a bacterium with hydrolytic activity against multiple seaweed-derived polysaccharides

Psychrosphaera algicola sp. nov. and Paraglaciecola algarum sp. nov., and reclassification of Pseudoalteromonas elyakovii, Pseudoalteromonas flavipulchra, and Pseudoalteromonas profundi as later heterotypic synonyms of P. distincta, P. maricaloris, and P. gelatinilytica

Two Gram-negative, obligately aerobic, rod-shaped bacteria, strains G1-22T and G1-23T, were isolated from the phycosphere of a marine brown alga. Both strains exhibited catalase- and oxidase-positive activities. Strain G1-22T displayed optimal growth at 25 °C, pH 8.0, and 2.0-3.0% (w/v) NaCl, while strain G1-23T exhibited optimal growth at 25 °C, pH 8.0, and 4.0% NaCl. Ubiquinone-8 was identified as the sole isoprenoid quinone in both strains. As major fatty acids (> 5%), strain G1-22T contained C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C12 : 1 3-OH, and C10 : 0 3-OH, while strain G1-23T contained C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), and C14 : 0. Phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol were major polar lipids in both strains. Strains G1-22T and G1-23T had DNA G+C contents of 40.2 and 38.9 mol%, respectively. Phylogenetic analyses based on 16S rRNA and genome sequences revealed that strains G1-22T and G1-23T formed distinct phylogenetic lineages within the genera Psychrosphaera and Paraglaciecola, respectively. Strain G1-22T showed closest relatedness to Psychrosphaera ytuae MTZ26T with 97.8% 16S rRNA gene sequence similarity, 70.2% average nucleotide identity (ANI), and a 21.5% digital DNA-DNA hybridization (dDDH) value, while strain G1-23T was most closely related to Paraglaciecola aquimarina KCTC 32108T with 95.6% 16S rRNA gene sequence similarity, 74.6% ANI, and a 20.1% dDDH value. Based on phenotypic and molecular characteristics, strains G1-22T and G1-23T are proposed to represent two novel species, namely Psychrosphaera algicola sp. nov. (type strain G1-22T=KACC 22486T=JCM 34971T) and Paraglaciecola algarum sp. nov. (type strain G1-23T=KACC 22490T=JCM 34972T), respectively. Additionally, based on the comparison of whole genome sequences, it is proposed that Pseudoalteromonas elyakovii, Pseudoalteromonas flavipulchra, and Pseudoalteromonas profundi are reclassified as later heterotypic synonyms of Pseudoalteromonas distincta, Pseudoalteromonas maricaloris, and Pseudoalteromonas gelatinilytica, respectively.

Identification of bacteria in potential mutualism with toxic Alexandrium catenella in Chilean Patagonian fjords by in vitro and field monitoring

The dinoflagellate Alexandrium catenella is a well-known paralytic shellfish toxin producer that forms harmful algal blooms, repeatedly causing damage to Chilean coastal waters. The causes and behavior of algal blooms are complex and vary across different regions. As bacterial interactions with algal species are increasingly recognized as a key factor driving algal blooms, the present study identifies several bacterial candidates potentially associated with Chilean Alexandrium catenella. This research narrowed down the selection of bacteria from the Chilean A. catenella culture using antibiotic treatment and 16S rRNA metabarcoding analysis. Subsequently, seawater from two Chilean coastal stations, Isla Julia and Isla San Pedro, was monitored for two years to detect Alexandrium species and the selected bacteria, utilizing 16S and 18S rRNA gene metabarcoding analyses. The results suggested a potential association between Alexandrium species and Spongiibacteraceae at both stations. The proposed candidate bacteria within the Spongiibacteraceae family, potentially engaging in mutualistic relationships with Alexandrium species, included the genus of BD1-7 clade, Spongiibbacter, and Zhongshania.

Biocatalytic Conversion of Carrageenans for the Production of 3,6-Anhydro-D-galactose

Marine biomass stands out as a sustainable resource for generating value-added chemicals. In particular, anhydrosugars derived from carrageenans exhibit a variety of biological functions, rendering them highly promising for utilization and cascading in food, cosmetic, and biotechnological applications. However, the limitation of available sulfatases to break down the complex sulfation patterns of carrageenans poses a significant limitation for the sustainable production of valuable bioproducts from red algae. In this study, we screened several carrageenolytic polysaccharide utilization loci for novel sulfatase activities to assist the efficient conversion of a variety of sulfated galactans into the target product 3,6-anhydro-D-galactose. Inspired by the carrageenolytic pathways in marine heterotrophic bacteria, we systematically combined these novel sulfatases with other carrageenolytic enzymes, facilitating the development of the first enzymatic one-pot biotransformation of ι- and κ-carrageenan to 3,6-anhdyro-D-galactose. We further showed the applicability of this enzymatic bioconversion to a broad series of hybrid carrageenans, rendering this process a promising and sustainable approach for the production of value-added biomolecules from red-algal feedstocks.

Fluctibacter corallii gen. nov., sp. nov., isolated from the coral Montipora capitata on a reef in Kāne'ohe Bay, O'ahu, Hawai'i, reclassification of Aestuariibacter halophilus as Fluctibacter halophilus comb. nov., and Paraglaciecola oceanifecundans as a later heterotypic synonym of Paraglaciecola agarilytica

Strain AA17T was isolated from an apparently healthy fragment of Montipora capitata coral from the reef surrounding Moku o Lo'e in Kāne'ohe Bay, O'ahu, Hawai'i, USA, and was taxonomically evaluated using a polyphasic approach. Comparison of a partial 16S rRNA gene sequence found that strain AA17T shared the greatest similarity with Aestuariibacter halophilus JC2043T (96.6%), and phylogenies based on 16S rRNA gene sequences grouped strain AA17T with members of the Aliiglaciecola, Aestuariibacter, Lacimicrobium, Marisediminitalea, Planctobacterium, and Saliniradius genera. To more precisely infer the taxonomy of strain AA17T, a phylogenomic analysis was conducted and indicated that strain AA17T formed a monophyletic clade with A. halophilus JC2043T, divergent from Aestuariibacter salexigens JC2042T and other related genera. As a result of monophyly and multiple genomic metrics of genus demarcation, strain AA17T and A. halophilus JC2043T comprise a distinct genus for which the name Fluctibacter gen. nov. is proposed. Based on a polyphasic characterisation and identifying differences in genomic and taxonomic data, strain AA17T represents a novel species, for which the name Fluctibacter corallii sp. nov. is proposed. The type strain is AA17T (= LMG 32603 T = NCTC 14664T). This work also supports the reclassification of A. halophilus as Fluctibacter halophilus comb. nov., which is the type species of the Fluctibacter genus. Genomic analyses also support the reclassification of Paraglaciecola oceanifecundans as a later heterotypic synonym of Paraglaciecola agarilytica.

Synergistic effects of temperature and light affect the relationship between Taonia atomaria and its epibacterial community: a controlled conditions study

In the context of global warming, this study aimed to assess the effect of temperature and irradiance on the macroalgal Taonia atomaria holobiont dynamics. We developed an experimental set-up using aquaria supplied by natural seawater with three temperatures combined with three irradiances. The holobiont response was monitored over 14 days using a multi-omics approach coupling algal surface metabolomics and metabarcoding. Both temperature and irradiance appeared to shape the microbiota and the surface metabolome, but with a distinct temporality. Epibacterial community first changed according to temperature, and later in relation to irradiance, while the opposite occurred for the surface metabolome. An increased temperature revealed a decreasing richness of the epiphytic community together with an increase of several bacterial taxa. Irradiance changes appeared to quickly impact surface metabolites production linked with the algal host photosynthesis (e.g. mannitol, fucoxanthin, dimethylsulfoniopropionate), which was hypothesized to explain modifications of the structure of the epiphytic community. Algal host may also directly adapt its surface metabolome to changing temperature with time (e.g. lipids content) and also in response to changing microbiota (e.g. chemical defences). Finally, this study brought new insights highlighting complex direct and indirect responses of seaweeds and their associated microbiota under changing environments.

Effect of polymer type on the colonization of plastic pellets by marine bacteria

Plastic is omnipresent in the oceans and serves as a surface for biofilm-forming microorganisms. Plastic debris comprises different polymers, which may influence microbial colonization; here, we evaluated whether polymer type affects bacterial biofilm formation. Quantifying the biofilm on polyethylene (PE), polypropylene (PP) or polystyrene (PS) pellets by six marine bacterial strains (Vibrio,Pseudoalteromonas,Phaeobacter) demonstrated that each strain had a unique colonization behavior with either a preference for PS or PP over the other polymer types or no preference for a specific plastic type. PE, PP and PS pellets were exposed to natural seawater microbiota using free-living or total communities as inoculum. Microbial assembly as determined by 16S rRNA (V4) amplicon sequencing was affected by the composition of the initial inoculum and also by the plastic type. Known polymer and hydrocarbon degraders such as Paraglaciecola, Oleibacter and Hydrogenophaga were found in the plastic biofilms. Thus, on a community level, bacterial colonization on plastic is influenced by the microorganisms as well as the polymer type, and also individual strains can demonstrate polymer-specific colonization.

Paraglaciecola marina sp. nov., isolated from marine alga (Sargassum natans (L.) Gaillon)

A novel Gram-stain-negative, straight or curved rod-shaped, non-spore-forming, strictly aerobic, motile bacterium with a single polar flagellum, designated D3211T, was isolated from marine alga collected at the seashore of Yantai, PR China. The organism grew optimally at 24 °C, pH 7.0 and in the presence of 2.0 % (w/v) NaCl. Strain D3211T contained ubiquinone 8 as the major respiratory quinone and C16 : 1  ω7c and/or C16 : 1  ω6c, C16 : 0, iso-C17 : 0 and anteiso-C17 : 1 B and/or iso-C17 : 1 I as the major fatty acids. The predominant polar lipids of strain D3211T were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The DNA G+C content of strain D3211T was 39.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that the novel strain was related most closely to Paraglaciecola arctica BSs20135T, Paraglaciecola aestuariivivens JDTF-33T, Paraglaciecola aquimarina KCTC 32108T, Paraglaciecola mesophila DSM 15026T, Paraglaciecola psychrophila JCM 13954T and Paraglaciecola polaris ARK 150T with 97.6, 97.6, 97.5, 97.4, 97.3 and 97.1 % sequence similarities, respectively. Calculated average nucleotide identity and DNA-DNAhybridization values between strain D3211T and its phylogenetically related Paraglaciecola species were in the range 70.2-73.4 % and 19.1-20.4 %, respectively. On the basis of polyphasic analyses, strain D3211T represents a novel species of the genus Paraglaciecola, for which the name Paraglaciecola marina sp. nov. is proposed. The type strain is D3211T (=KCTC 72122T=MCCC 1K03603T).

Marisediminitalea mangrovi gen. nov., sp. nov., isolated from marine mangrove sediment, and reclassification of Aestuariibacter aggregatus as Marisediminitalea aggregata comb. nov

Strain GS-14^T was isolated from a mangrove sediment sample collected at Beilun Estuary National Nature Reserve, Guangxi Province, PR China. Cells were Gram-stain-negative, strictly aerobic and rod-shaped with a polar flagellum. Optimal growth occurred in the presence of 3-6 % (w/v) NaCl, at pH 6-8 and at a temperature of 37 °C. The predominant polar lipids were phosphatidylglycerol and phosphatidylethanolamine. Ubiquinone 8 (Q-8) was the sole respiratory quinone. The major fatty acids (>10 % of the total fatty acids) were summed feature 3 (C_16 : 1ω7c and/or C_16 : 1ω6c) and C_16 : 0. The DNA G+C content was 47.6 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain GS-14^T had the highest sequence similarity to Aestuariibacter aggregatus WH169^T (96.63 %), Aliiglaciecola coringensis AK49^T (96.56 %) and Alteromonas lipolytica JW12^T (96.22 %). In addition, the OrthoANIu value and dDDH values calculated from the genomes of strain GS-14^T and A. aggregatus WH169^T were 79.5 and 21.9 %, respectively. Based on the polyphasic taxonomic results, strain GS-14^T is considered to represent a novel species in a new genus, for which the name Marisediminitalea mangrovi gen. nov., sp. nov. is proposed. The type strain of Marisediminitalea mangrovi is GS-14^T (=KCTC 72401^T=MCCC 1K03622^T). Because Aestuariibacter aggregatus WH169^T clustered with strain GS-14^T in the phylogenetic trees and was clearly separated from the two species within the genus Aestuariibacter, it is reclassified as a member of the genus Marisediminitalea as Marisediminitalea aggregata comb. nov. (type strain WH169^T=CGMCC 1.8995^T=LMG 25283^T). The type species of the genus Marisediminitalea is Marisediminitalea aggregata gen. nov., comb. nov.

Identification and Characterization of a β-N-Acetylhexosaminidase with a Biosynthetic Activity from the Marine Bacterium Paraglaciecola hydrolytica S66T

β-N-Acetylhexosaminidases are glycoside hydrolases (GHs) acting on N-acetylated carbohydrates and glycoproteins with the release of N-acetylhexosamines. Members of the family GH20 have been reported to catalyze the transfer of N-acetylglucosamine (GlcNAc) to an acceptor, i.e., the reverse of hydrolysis, thus representing an alternative to chemical oligosaccharide synthesis. Two putative GH20 β-N-acetylhexosaminidases, PhNah20A and PhNah20B, encoded by the marine bacterium Paraglaciecola hydrolytica S66^T, are distantly related to previously characterized enzymes. Remarkably, PhNah20A was located by phylogenetic analysis outside clusters of other studied β-N-acetylhexosaminidases, in a unique position between bacterial and eukaryotic enzymes. We successfully produced recombinant PhNah20A showing optimum activity at pH 6.0 and 50 °C, hydrolysis of GlcNAc β-1,4 and β-1,3 linkages in chitobiose (GlcNAc)₂ and GlcNAc-1,3-β-Gal-1,4-β-Glc (LNT2), a human milk oligosaccharide core structure. The kinetic parameters of PhNah20A for p-nitrophenyl-GlcNAc and p-nitrophenyl-GalNAc were highly similar: k_cat/K_M being 341 and 344 mM⁻¹·s⁻¹, respectively. PhNah20A was unstable in dilute solution, but retained full activity in the presence of 0.5% bovine serum albumin (BSA). PhNah20A catalyzed the formation of LNT2, the non-reducing trisaccharide β-Gal-1,4-β-Glc-1,1-β-GlcNAc, and in low amounts the β-1,2- or β-1,3-linked trisaccharide β-Gal-1,4(β-GlcNAc)-1,x-Glc by a transglycosylation of lactose using 2-methyl-(1,2-dideoxy-α-d-glucopyrano)-oxazoline (NAG-oxazoline) as the donor. PhNah20A is the first characterized member of a distinct subgroup within GH20 β-N-acetylhexosaminidases.

Agarolytic culturable bacteria associated with three antarctic subtidal macroalgae

Bacterial communities of Antarctic marine macroalgae remain largely underexplored in terms of diversity and biotechnological applications. In this study, three Antarctic subtidal macroalgae (Himantothallus grandifolius, Pantoneura plocamioides and Plocamium cartilagineum), two of them endemic of Antarctica, were investigated as a source for isolation of agar-degrading bacteria. A total of 21 epiphytic isolates showed agarolytic activity at low temperature on agar plates containing agar as the sole carbon source. 16S rRNA identification showed that the agar-degrading bacteria belonged to the genera Cellulophaga, Colwellia, Lacinutrix, Olleya, Paraglaciecola, Pseudoalteromonas and Winogradskyella. The agarase enzyme from a potential new species of the genus Olleya was selected for further purification. The enzyme was purified from the culture supernatant of Olleya sp. HG G5.3 by ammonium sulfate precipitation and ion-exchange chromatography. Molecular weight of the agarase was estimated to be 38 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme exhibited activity at 4 °C, retaining > 50% of its maximum activity at this temperature. This is the first study reporting the phylogeny of agar-degrading bacteria isolated from Antarctic subtidal macroalgae and the results suggest the huge potential of Antarctic algae-associated bacteria as a source of cold-active hydrolytic enzymes of biotechnological interest.

A Novel Enzyme Portfolio for Red Algal Polysaccharide Degradation in the Marine Bacterium Paraglaciecola hydrolytica S66T Encoded in a Sizeable Polysaccharide Utilization Locus

Marine microbes are a rich source of enzymes for the degradation of diverse polysaccharides. Paraglaciecola hydrolytica S66^T is a marine bacterium capable of hydrolyzing polysaccharides found in the cell wall of red macroalgae. In this study, we applied an approach combining genomic mining with functional analysis to uncover the potential of this bacterium to produce enzymes for the hydrolysis of complex marine polysaccharides. A special feature of P. hydrolytica S66^T is the presence of a large genomic region harboring an array of carbohydrate-active enzymes (CAZymes) notably agarases and carrageenases. Based on a first functional characterization combined with a comparative sequence analysis, we confirmed the enzymatic activities of several enzymes required for red algal polysaccharide degradation by the bacterium. In particular, we report for the first time, the discovery of novel enzyme activities targeting furcellaran, a hybrid carrageenan containing both β-carrageenan and κ/β-carrageenan motifs. Some of these enzymes represent a new subfamily within the CAZy classification. From the combined analyses, we propose models for the complete degradation of agar and κ/β-type carrageenan by P. hydrolytica S66^T. The novel enzymes described here may find value in new bio-based industries and advance our understanding of the mechanisms responsible for recycling of red algal polysaccharides in marine ecosystems.

Neptunicella marina gen. nov., sp. nov., isolated from surface seawater

A Gram-stain-negative, aerobic, short rod-shaped bacterium with a single polar flagellum, designated strain S27-2^T, was isolated from surface seawater from the Indian Ocean. Growth was observed in 0-12.0 % (w/v) NaCl with an optimum of 0.5-2.0 % (w/v) NaCl, pH 6.0-9.0 with an optimum of pH 7.0, and growth temperature of 10-41 °C with an optimum of 25-37 °C. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S27-2^T belonged to the family Alteromonadaceae and formed a distinct lineage with the type strain of Pseudobowmanella zhangzhouensis. Levels of 16S rRNA gene sequence similarity between strain S27-2^T and members of related genera included in the trees ranged from 86.7 to 93.8 %. Strain S27-2^T contained Q-8 as the predominant ubiquinone. The principal fatty acids (>10 %) were C16 : 0 (22.1 %), C16 : 1ω7c/ω6c (22.7 %) and C18 : 1ω7c/ω6c (20.1 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified phospholipid and two unknown lipids. The G+C content of strain S27-2^T was 43.7 mol%. On the basis of the polyphasic taxonomic evidence presented in this study, strain S27-2^T should be classified as a novel species in a new genus within the family Alteromonadaceae, for which the name Neptunicella marina gen. nov., sp. nov. is proposed, with the type strain S27-2^T (= KCTC52335^T=MCCC 1A02149^T).