Suk Min Kim

Metabolic pathway of 3,6-anhydro-L-galactose in agar-degrading microorganisms

Recently, agarose-containing macroalgae have gained attention as possible renewable sources for bioethanol-production because of their high polysaccharide content. Complete hydrolysis of agarose produces two monomers, D-galactose (D-Gal) and 3,6-anhydro-L-galactose (L-AnG). However, at present, bioethanol yield from agarophyte macroalgae is low due to the inability of bioethanolproducing microorganisms to convert non-fermentable sugars, such as L-AnG, to bioethanol. Therefore, to increase the bioethanol productivity of agarophytes, it is necessary to determine how agar-degrading microorganisms metabolize L-AnG, and accordingly, construct recombinant microorganisms that can utilize both D-Gal and L-AnG. Previously, we isolated a novel microorganism belonging to a new genus, Postechiella marina M091, which hydrolyzes and metabolizes agar as the carbon and energy source. Here, we report a comparative genomic analysis of P. marina M091, Pseudoalteromonas atlantica T6c, and Streptomyces coelicolor A3(2), of the classes Flavobacteria, Gammaproteobacteria, and Actinobacteria, respectively. In this bioinformatic analysis of these agarolytic bacteria, we found candidate common genes that were believed to be involved in L-AnG metabolism. We then experimentally confirmed the enzymatic function of each gene product in the L-AnG cluster. The formation of two key intermediates, 2-keto-3-deoxy-L-galactonate and 2-keto-3-deoxy-D-gluconate, was also verified using enzymes that utilize these molecules as substrates. Combining bioinformatic analysis and experimental data, we showed that L-AnG is metabolized to pyruvate and D-glyceraldehyde-3-phosphate via six enzymecatalyzed reactions in the following reaction sequence: 3,6-anhydro-L-galactose → 3,6-anhydro-L-galactonate → 2-keto-3-deoxy-L-galactonate → 2,5-diketo-3-deoxy-L-galactonate → 2-keto-3-deoxy-D-gluconate → 2-keto-3-deoxy-6-phospho-D-gluconate → pyruvate + D-glyceraldehyde-3- phosphate. To our knowledge, this is the first report on the metabolic pathway of L-AnG degradation.

Winogradskyella damuponensis sp. nov., isolated from seawater

A novel bacterium, designated F081-2(T), isolated from seawater from Damupo beach in Pohang, Korea, was investigated using a polyphasic taxonomic approach. Cells were yellow-pigmented, strictly aerobic, motile by gliding, Gram-negative-staining and rod-shaped. The temperature, pH and NaCl ranges for growth were 4-35 °C, pH 5.5-9.5 and 1.0-5.0 %, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain F081-2(T) belonged to a distinct lineage in the genus Winogradskyella of the family Flavobacteriaceae, sharing 93.7-98.1 % similarity with recognized members of the genus. Low levels of DNA-DNA relatedness values were found between strain F081-2(T) and Winogradskyella eximia KCTC 12219(T) (61.1 %), Winogradskyella thalassocola KCTC 12221(T) (47.0 %), Winogradskyella echinorum KCTC 22026(T) (39.3 %), Winogradskyella rapida CCUG 56098(T) (34.3 %) and Winogradskyella arenosi JCM 17633(T) (33.4 %). The major cellular fatty acids were iso-C(15 : 0) (25.3 %), iso-C(15 : 1) G (14.6 %), iso-C(17 : 0) 3-OH (9.3 %), anteiso-C(15 : 0) (7.8 %) and iso-C(15 : 0) 3-OH (7.6 %). The polar lipid profile was composed of phosphatidylethanolamine, one unidentified aminolipid, one unidentified phospholipid, one unidentified aminophospholipid and six unidentified lipids. The major respiratory quinone was menaquinone-6 and the DNA G+C content of the strain was 32.3 mol%. On the basis of phenotypic, phylogenetic and genotypic data, strain F081-2(T) represents a novel species within the genus Winogradskyella, for which the name Winogradskyella damuponensis sp. nov. is proposed. The type strain is F081-2(T) (=KCTC 23552(T) = JCM 17633(T)).

Postechiella marina gen. nov., sp. nov., isolated from seawater.

A Gram-staining-negative, strictly aerobic, non-motile, yellow-pigmented bacterium, designated strain M091(T), was isolated from seawater at Damupo beach in Pohang, Republic of Korea, and investigated using a polyphasic taxonomic approach. The novel strain grew optimally at 25 °C, pH 7.0-8.0, and in the presence of 3% (w/v) NaCl. In a phylogenetic analysis based on 16S rRNA gene sequences, strain M091(T) formed a lineage within the family Flavobacteriaceae that was distinct from the most closely related genera of Flaviramulus (95.1% sequence similarity), Algibacter (94.9-93.9%), Mariniflexile (94.8-94.2%), Winogradskyella (94.8-93.2%), Lacinutrix (94.7-93.8%) and Tamlana (94.7-92.9%). The polar lipid profile of the novel strain comprised phosphatidylethanolamine, two unidentified aminolipids, one unidentified phospholipid and seven unidentified lipids. The predominant cellular fatty acids were iso-C(15:0) (20.5%), iso-C(17:0) 3-OH (15.4%), iso-C(15:0) 3-OH (12.4%), C(15:0) (10.9%) and iso-C(15:1) G (9.9%). The genomic DNA G+C content of strain M091(T) was 34.4 mol% and the major respiratory quinone was MK-6. Based on phenotypic and genotypic data, strain M091(T) represents a new genus and novel species in the family Flavobacteriaceae, for which the name Postechiella marina gen. nov., sp. nov. is proposed. The type strain of the type species is M091(T) (=KCTC 23537(T)=JCM 17630(T)).

Lactic acid production from seaweed hydrolysate of Enteromorpha prolifera (Chlorophyta)

We examined the feasibility of using the green seaweed Enteromorpha prolifera as an alternative carbon source for chemical production. For this purpose, the chemical composition (proximate analysis, ultimate analysis, and mineral analysis) and acid hydrolysis of E. prolifera were investigated. In addition, lactic acid fermentation of E. prolifera hydrolysate was carried out using five Lactobacillus strains. The lactic acid yield, which is defined as the ratio of the lactic acid production to total sugar consumption, varied depending on the strains. Lactobacillus salivarius showed the highest lactic acid yield (68.5%), followed by Lactobacillus plantarum (66.0%), Lactobacillus rhamnosus (55.8%), Lactobacillus brevis (54.5%), and Lactobacillus casei (51.4%). The results shown in this study imply that E. prolifera would be competitive with lignocellulosic biomass such as corn stover in terms of lactic acid production yield and that green seaweed can be used as a feedstock for industrial production of chemicals.

Psychroserpens damuponensis sp. nov., isolated from seawater

A novel bacterium, designated strain F051-1(T), isolated from a seawater sample collected from the coast at Damupo beach in Pohang, Korea, was investigated in a polyphasic taxonomic study. Cells were yellow-pigmented, strictly aerobic, Gram-staining-negative and rod-shaped. The temperature, pH and NaCl ranges for growth were 4-30 °C, pH 6.0-9.0 and 1.0-6.0 % (w/v), respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain F051-1(T) belongs to the genus Psychroserpens in the family Flavobacteriaceae. Its closest relatives were Psychroserpens burtonensis ACAM 188(T) (96.8 % 16S rRNA gene sequence similarity) and Psychroserpens mesophilus KOPRI 13649(T) (95.7 %). The major cellular fatty acids were iso-C(15 : 0), iso-C(15 : 1) G and anteiso-C(15 : 0). The polar lipid profile consisted of a mixture of phosphatidylethanolamine, two unidentified aminolipids, one unidentified phospholipid and eight unidentified lipids. The major respiratory quinone was menaquinone-6 and the genomic DNA G+C content of the strain was 33.5 mol%. On the basis of phenotypic, phylogenetic and genotypic data, strain F051-1(T) represents a novel species within the genus Psychroserpens, for which the name Psychroserpens damuponensis sp. nov. is proposed. The type strain is F051-1(T) ( = KCTC 23539(T)  = JCM 17632(T)).

Genome Sequence of the Unclassified Marine Gammaproteobacterium BDW918

The unclassified marine gammaproteobacterium BDW918, which utilizes volatile fatty acids but not most common carbohydrates and amino acids, was isolated from Dokdo seawater in South Korea. Here we present a draft genome of the strain BDW918, which encodes many putative genes related to fatty acid metabolism and aromatic hydrocarbon degradation.

Sagittula marina sp. nov., isolated from seawater and emended description of the genus Sagittula

A novel bacterium, designated strain F028-2(T), was isolated from seawater at Damupo beach in Pohang, Korea, and investigated in a taxonomic study using a polyphasic approach. This novel strain was strictly aerobic, non-motile, Gram-stain-negative and rod-shaped, and occasionally formed aggregates. The temperature, pH and NaCl ranges for growth were 4-30 °C, pH 6.5-9.0 and 1-7% (w/v), respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain F028-2(T) formed a lineage within the family Rhodobacteraceae of the class Alphaproteobacteria, and was closely related to members of the genera Sagittula and Antarctobacter with 96.3-96.4% sequence similarities. The polar lipid profile of strain F028-2(T) comprised diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids, one unidentified phospholipid and six unidentified lipids. The predominant cellular fatty acids were C18:1ω7c and C12:1 3-OH. The genomic DNA G+C content of strain F028-2(T) was 61.6 mol% and the major respiratory quinone was Q-10. Based on phenotypic, phylogenetic and genotypic data, strain F028-2(T) is considered to represent a novel species in the genus Sagittula, for which the name Sagittula marina sp. nov. is proposed. The type strain is F028-2(T) (=KCTC 23543(T)=JCM 17627(T)). An emended description of the genus Sagittula is also proposed.