Genus specific unusual carotenoids in purple bacteria, Phaeospirillum and Roseospira: structures and biosyntheses

The Methoxylated, Highly Conjugated C40 Carotenoids, Spirilloxanthin and Anhydrorhodovibrin, Can Be Separated Using High Performance Liquid Chromatography with Safe and Environmentally Friendly Solvents

High performance liquid chromatography (HPLC) is a frequently used technique in carotenoid research. So far, however, little attention has been paid to the fact that many of the organic solvents used in HPLC separation of highly apolar C₄₀ carotenoids impose a significant threat to both health (especially for women) and the general laboratory environment. Here, we developed a solvent combination capable of allowing high-resolution HPLC separation of the C₄₀ carotenoid, spirilloxanthin, and all of its biosynthetic precursors beginning with phytoene, using relatively safe, environmentally friendly solvents. We show that separation of spirilloxanthin and its precursors anhydrorhodovibrin and lycopene using modern ultra-high performance chromatography (UHPLC) poses particular problems for apolar carotenoid separation, due to the long residence times in the sample delivery system, which facilitates carotenoid aggregation. We resolved these problems by developing the solvent delivery combination acetone/acetonitrile/isopropanol/methanol (65/30/5/2 (v/v/v/v)), which allows excellent column separation using the safe isocratic solvent system methanol/tetrahydrofuran (98/2 (v/v)). We also demonstrate that the development strategy for optimizing a solvent system for carotenoid separation can be well-described by the use of the average dielectric constant of the total sample delivery solvent, and present a formal method for analysis of the efficiency of separation.

The influence of protozoa with a filtered and non-filtered seawater culture of Tetraselmis sp., and effects to the bacterial and algal communities over 10 days

In this study a filter was used to remove protozoa and its effects on a Tetraselmis sp. culture were evaluated in terms of final total lipid, final total dry weight, cell counts, and both the bacterial and algal communities. The protozoa species observed within this study was identified as Cohnilembus reniformis. It was observed that on the final day no C. reniformis were present in filtered cultures compared to the non-filtered culture which contained 40±3 C. reniformis/mL. The presence of C. reniformis within the culture did not affect the total lipid or the total dry weight recovered, suggesting that Tetraselmis sp. was capable of surviving and growing in the presence of C. reniformis. Overall it is suggested that an 11 μm filter was effective at removing protozoa, though growing a microalgae culture without filtration did not show any significant effect.

Phaeospirillum tilakii sp. nov., a phototrophic alphaproteobacterium isolated from aquatic sediments

Two strains (JA492T and JA590) of spiral-shaped, anaerobic, Gram-stain-negative, motile, purple non-sulfur bacteria were isolated from aquatic sediments from a bird sanctuary and a stream, respectively, and were characterized by a polyphasic taxonomic approach. Bacteriochlorophyll a and carotenoids (rhodopin, lycopene, hydroxylycopene glucoside and dihydroxylycopene diglucoside) were present as photosynthetic pigments. Intracellular photosynthetic membranes were of the stacked type. The major fatty acids were C18 : 1ω7c, C16 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) in both strains. Ubiquinones and menaquinones were present as major quinone components. The genomic DNA G+C contents of strains JA492T and JA590 were 63.8 and 61.5 mol%, respectively. Both strains were closely related (mean DNA–DNA hybridization >70 %). Phylogenetic analysis showed that the strains clustered with species of the genus Phaeospirillum of the family Rhodospirillaceae , class Alphaproteobacteria . Based on 16S rRNA gene sequence analysis, both strains showed highest sequence similarity with Phaeospirillum oryzae JA317T (97.2–97.4 %), Phaeospirillum molischianum DSM 120T (96.5–96.7 %), Phaeospirillum fulvum DSM 113T (96.7–96.9 %) and Phaeospirillum chandramohanii JA145T (96.5–96.7 %). DNA–DNA relatedness between strain JA492T and its closest relative in the genus Phaeospirillum was less than 42 %. It is evident from phenotypic, chemotaxonomic and molecular genetic data that strain JA492T represents a novel species of the genus Phaeospirillum , for which the name Phaeospirillum tilakii sp. nov. is proposed; the type strain is JA492T ( = NBRC 107650T = KCTC 15012T).