Rheinheimera japonica sp. nov., a novel bacterium with antimicrobial activity from seashore sediments of the Sea of Japan.

Two gram-negative, aerobic, brown-pigmented, motile rod-shaped bacteria KMM 9512 and KMM 9513(T) were isolated from a sediment sample collected from the Sea of Japan seashore, Russia. On the basis of the 16S rRNA gene sequence analysis, novel strains KMM 9512 and KMM 9513(T) positioned within the genus Rheinheimera (class Gammaproteobacteria) as a separate subline adjacent to Rheinheimera baltica DSM 14885(T) sharing highest gene sequence similarities of 98.6-97.6 % to their closest phylogenetic relatives, Rheinheimera muenzenbergensis LMG 27269(T), R. baltica DSM 14885(T), Rheinheimera aquimaris JCM 14331(T), Rheinheimera nanhaiensis KACC 14030(T), and Rheinheimera pacifica KMM 1406(T). Strains KMM 9512 and KMM 9513(T) belong to the same separate genospecies on the basis of the 16S rRNA gene sequence similarity (99.8 %) and their DNA relatedness to each other (89 %) and to closely related Rheinheimera species (25-53 %). The major isoprenoid quinone was Q-8, polar lipids consisted of phosphatidylserine, phosphatidylglycerol, phosphatidylethanolamine, unknown aminolipids, unknown aminophospholipids, unknown phospholipids, and unknown lipids, and major fatty acid were C16:0, C16:1 ω7c, C17:1 ω8c, C12:0 3-OH followed by C17:0 and C18:1 ω7c in both strains. Strains KMM 9512 and KMM 9513(T) revealed a remarkable antagonistic activity toward a number of gram-positive and gram-negative microorganisms. On the basis of phylogenetic analysis, DNA-DNA hybridization results, and phenotypic differences, strains KMM 9512 and KMM 9513(T) are proposed to be classified as a novel species of the genus Rheinheimera, Rheinheimera japonica sp. nov. The type strain of this species is KMM 9513(T) = NRIC 0918(T).

Characterization of unusual alkaliphilic gram-positive bacteria isolated from degraded brown alga thalluses.

Two orange-pigmented Gram-positive, aerobic bacteria were isolated from enrichment culture during degradation of brown alga Fucus evanescens thalluses. In this work, atomic force microscopy (AFM) has been used to study the cell morphology. The non-contact mode imaging revealed unusual irregular coccoid shape of cells, possessing a single flagellum. Bacteria produced carotenoid pigments, were chemo-organotrophic, alkaliphilic and halo-tolerant growing well on nutrient media containing up to 15% NaCl. Growth temperature ranged from 5 to 45 degrees C. The DNA base compositions were 48 mol% G + C and the level of DNA similarity of two strains was conspecific (98%). A comparative phylogenetic analysis of 16S rRNA gene sequences revealed that the strain KMM 3738 tightly clustered with recently described Planococcus maritimus (99.9% 16S rRNA gene sequence similarity). DNA-DNA hybridisation experiments revealed that DNA from the KMM 3738 showed 12-15% and 16-35% of genetic relatedness with the DNA of type strains of the genera Planomicrobium and Planococcus, respectively, and 87% with DNA from Planococcus maritimus, indicating that new isolates belong to the later species.

The membranotropic activity of cyclic acyldepsipeptides from bacterium Bacillus pumilus, associated with the marine sponge Ircinia sp.

The isolate of Bacillus pumilus associated with the marine sponge Ircinia sp. produced the surfactin-like lipopeptides, cyclic acyldepsipeptides. The hemolytic activity of individual cyclic acyldepsipeptides, bacircines (BI) 2, 3, 4, 5 and 5A having different acyl side chain structures (anteiso-C13, iso-C14, normal-C14, anteiso-C15, and iso-C15, respectively) was studied. The hemolytic power of bacircines depended on both the structure of the side chain (n->iso->anteiso-) and pH values (5.6 and 6.5 > 7.4). Hemolytic potency as a function of BI 5 concentration was given for pH 6.5; 7.4; 8.0; 9.0. pH dependent hemolysis induced by BI 5 was shown to be reversible. The membrane damaging potential of bacircine 5 (5 microM) at pH 6.5 was characterized by a higher rate of hemolysis and by a shorter time between the introduction of BI 5 solution into the RBC samples and the onset of hemolysis. Under this condition, BI 5 decreased abnormally the microviscosity of erythrocyte ghosts bilayer. The damaging potency of BI 5 decreased with an increase pH from 6.5 to 7.4 or its decrease from 6.5 to 4.9. It was shown that fatty acid bacircine fragment penetrated into the lipid bilayer to a depth of minimum 7 carbon atoms. Constants of dissociation of the Asp (pK 4.75) and Glu (pK 6.65) residues of bacircine in the lipid bilayer were obtained. These results showed that at pH 6.5 BI 5 possessed membranotropic activity in the monoionic form.

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. METHODS AND RESULTS: The kinetics of growth and haemolytic activities was investigated on sea-salts and NaCl-based nutrient media supplemented with either starch, or KBr over a period of 140 h. The first haemolytic activity occurred when bacterial cells reached the late stationary phase. The second haemolytic activity was observed in marine broth (MB) after 110 h of incubation. Addition of Fe to the culture medium neither affected bacterial growth nor reduced the haemolytic activity. However, the activity was enhanced in the presence of iron chelator. The second haemolytic activity was not affected by Ca2+, or inhibited by chymotrypsin or EDTA. CONCLUSIONS: The production of haemolysins by P. issachenkonii was greater on MB and was dependent on both the medium composition and time of incubation. The second haemolytic activity was heat stable, nonproteinaceous, calcium-independent and was regulated by Fe. SIGNIFICANCE AND IMPACT OF THE STUDY: The results demonstrated the importance of optimization of both the media composition and monitoring the haemolytic activity over a prolonged cultivation time to detect different types of haemolysins.