Yulia V. Alexeeva

Low-molecular-weight, biologically active compounds from marine Pseudoalteromonas species

We have examined the ability of marine Proteobacteria from the Pseudoalteromonas genus and Alteromonas macleodii to produce low-molecular-weight, biologically active compounds with antimicrobial and surface-active properties. A new marine bacterium, Pseudoalteromonas issachenkonii, exhibited a high level of biological activity and produced antifungal and hemolytic compounds. A detailed spectroscopic investigation based on UV, IR, high-resolution mass spectrometry, and 2D 1H and 13C nuclear magnetic resonance revealed that the former was indole-2,3-dione (isatin). The chemical structure of red-brown pigment (C9H7N3OS3) responsible for hemolytic activity remained unclear. Four of the 15 strains studied (P. luteoviolacea, P. rubra, P. undina, and P. issachenkonii) produced cell-bound, two (P. elaykovii and P. carrageenovora) produced extracellular, and one strain (P. citrea) produced cell-bound and extracellular fatty acids and phospholipids with surface activity. Neither peptides nor glycolipids with surface activity were detected.

Two species of culturable bacteria associated with degradation of brown algae Fucus Evanescens

The heterotrophic microbial enrichment community established during degradation of brown algae Fucus evanescens was characterized. A two-species bacterial community of marine culturable gamma-proteobacteria consisted of Pseudoalteromonas and Halomonas. The first member of the community, Pseudoalteromonas sp., was highly metabolically active, had bacteriolytic and hemolytic activities, produced proteinases (gelatinase and caseinase), lipases, DNases, and fucoidanhydrolases, laminaranases, alginases, pustulanases, beta-glucosidases, beta-galactosidases, beta-N-acetylglucosaminidases, and beta-xylosidases. The second member of the community, Halomonas marina, produced only caseinase and DNase, and it did not hydrolyze algal polysaccharides. Both members of the studied bacterial community utilized a range of easily assimilable monosaccharides and other low molecular weight organic substances. The results provide an evidence of the complex metabolic interrelations between two members of this culturable community. One of them Pseudoalteromonas sp., most likely plays the major role in the initial stages of algal degradation; the other one, H. marina, resistant to the bacteriolytic activity of the former, is able to utilize the products of degradation of polysaccharides.

Ecophysiological variabilities in Ectohydrolytic enzyme activities of some Pseudoalteromonas species, P. citrea, P. issachenkonii, and P. nigrifaciens

The ecophysiological variabilities in the ectohydrolytic enzyme profiles of the three species of Pseudoalteromonas, P. citrea, P. issachenkonii, and P. nigrifaciens, have been investigated. Forty-one bacteria isolated from several invertebrates, macroalgae, sea grass, and the surrounding water exhibited different patterns of hydrolytic enzyme activities measured as the hydrolysis of either native biopolymers or fluorogenic substrates. The activities of the following enzymes were assayed: proteinase, tyrosinase, lipase, amylase, chitinase, agarase, fucoidan hydrolase, laminaranase, alginase, pustulanase, cellulase, β-glucosidase, α- and β-galactosidases, β-N-acetylglucosaminidase, β-glucosaminidase, β-xylosidase, and α-mannosidase. The occurrence and cell-specific activities of all enzymes varied over a broad range (from 0 to 44 μmol EU per hour) and depended not only on taxonomic affiliation of the strain, but also on the source/place of its isolation. This suggests ‘specialization’ of different species for different types of polymeric substrates as, for example, all strains of P. citrea and P. issachenkonii hydrolyzed alginate and laminaran, while strains of P. nigrifaciens were lacking the ability to hydrolyze most of the algal polysaccharides. The incidence of certain enzymes such as fucoidan hydrolases, alginate lyases, agarases, and α-galactosidases might be strain specific and reflect its particular ecological habitat.

Optimization of glycosidases production by Pseudoalteromonas issachenkonii KMM 3549T

Aims: The present work aimed to design an optimized medium to yield a higher production of glycosides by Pseudoalteromonas issachenkonii KMM 3549T. 
Methods and Results: Higher levels of fucoidan hydrolase, alginase, laminaranase and b‐N‐acetylglucosaminidase production were obtained with peptone concentrations ranging from 2·5 g l−1 to 10 g l−1, while the presence of both yeast extract and glucose did not affect enzyme production. The activity of fucoidan hydrolase and laminaranase increased up to 4·83 µM h−1 mg−1 and 19·23 µM h−1 mg−1 protein, respectively, in growth media containing xylose (1·0 g l−1), laminarin (0·5 g l−1) or alginate (0·5 g l−1), and production of b‐N‐acetylglucosaminidase substantially increased in the presence of fucoidan (0·5 g l−1) or galactose (1 g l−1). All polysaccharides tested in concentrations of 0·5 g l−1 fucoidan and 0·2 g l−1 fucose induced production of alginase (up to 5·06 µM h−1 mg−1 protein). 
Conclusions: The production of glycosidases is not only stimulated by the presence of algal polysaccharides, but may also be stimulated by monosaccharides (e.g. xylose). 
Significance and Impact of the Study: The production of glycosidases by Pseudoalteromonas issachenkonii KMM 3549T was significantly improved by using a simple nutrient medium containing peptone (2·5 g l−1) and xylose (5·0 g l−1) in 100% natural seawater.

“Pseudoalteromonas januaria” SUT 11 as the Source of Rare Lipodepsipeptides

The marine bacterium “Pseudoalteromonasjanuaria” SUT 11 isolated from a seawater sample produced the rare cell-bound cyclic lipodepsipeptides A/A′, B/B′, and C/C′. The matrix-assisted laser desorption/ionization mass spectra indicated that one bromine atom presented in the peptides B/B′ and C/C′, whereas the component A/A′ contained no bromine atom. The acyldepsipeptides A/A′–C/C′ have an identical amino acid sequence, Thr-Val-Asn-Asn-Leu/allo-Ile, but differed in C-terminal amino acid and acyl moieties. Peptides A–C have Leu as a C-terminal amino acid, whereas peptides A′-C′ have allo-Ile. Acyl moieties in peptides A/A′, B/B′, and C/C′ have been found to consist of 11-(4′-hydroxyphenyl)-undeca-2,4,6,8,10-pentaenic acid, 9-(3′-bromo-4′-hydroxyphenyl)-nona-2,4,6,8-tetraenic acid, and 11-(3′-bromo-4′-hydroxyphenyl)-undeca-2,4,6,8,10-pentaenic acid, respectively. The structure of a main pair of peptides B/B′ with molecular masses 843/845 Da has been determined by means of ultraviolet, infrared, and two-dimensional nuclear magnetic resonance spectroscopy. We have demonstrated that tandem nano-electrospray ionization mass spectrometry is a very efficient way for the fast and sensitive investigation of lipopeptides A/A′ and C/C′ with molecular masses 791 and 869/871 Da, respectively, which have been isolated in small amounts.

Impact of cultivation conditions on haemolytic activity of Pseudoalteromonas issachenkonii KMM 3549T

Aims:  The present work aimed to study the effects of cultivation conditions on the haemolytic activities of Pseudoalteromonas issachenkonii.

Controlled self-assembly of actin filaments for dynamic biodevices

We investigated the immobilization of actin filaments and its self-assembly in vitro in a continuous-flow system on poly(styrene-maleic acid) (PSMA), poly(methyl methacrylate) (PMMA), poly(t-butyl methacrylate) [P(tBuMA)] polymeric surfaces and along the linear channels. Among these polymeric surfaces, PSMA appeared to be more suitable for supramolecular manipulations as it lacked inherent fluorescence, had good biocompatibility with actin-myosin, and provided sufficient amounts of binding sites for the covalent immobilization of actin. Covalent attachment of G-actin on PSMA polymeric surfaces resulted in stable polymerization followed by alignment of filaments over 1.5 h, along with a greater surface density of the proteins. It is shown that electrostatic condensation of intact F-actin filaments and F-actin/gelsolin filaments with Ba2+ can be successfully used for progressive bundle formation and alignment in the constant flow. Actin bundles retained their ability to support HMM-anti-HMM bead translocation. Long-range cooperative transitions in actin induced by gelsolin represent a structural perturbation of the barbed end and presumably result in regularly organized bundles that secure directional movement. This simple technique for fabrication of self-assembled and aligned F-actin/gelsolin bundles provides a convenient experimental system for nanotechnological applications.