Characterization of halophilic C50 carotenoid-producing archaea isolated from solar saltworks in Bohai Bay,China

Halophilic archaea comprise the majority of microorganisms found in hypersaline environments. C50 carotenoids accumulated in archaea cells are considered potential biotechnological products and possess a number of biological functions. Ten red colordes were isolated from brine water in a saltem crystaltizer pond of the Hangu Saltworks, China. 16S rRNA gene sequence analysis showed that the colonies belonged to the extremely halophilic archaea genera Halobacterium and Halorubrum. Two representative strains, Halobacterium strain SP-2 and Halorubrum strain SP-4, were selected for further study on the phenotypic characteristics and effects of salinity and pH on accumulation and composition of pigments in their cells. The archaeal strains were isolated and grown in a culture medium prepared by dissolving yeast extract （10 g/L） and acid-hydrolyzed casein （7.5 g/L） into brine water obtained from a I.ocal salt pond. Their optimum salinity and pH for growth were 250 and 7, respectively, although pigment accumulation （OD490/ mL broth） was highest at pH 8. In addition, at 150-300 salinity, increasing salinity resulted in decreasing pigment accumulation. Analysis of the UV-Vis spectrum, TLC and HLPC chromatograms showed that C50 carotenoid bacterioruberin is the major pigment in both strains.     

On the red coloration of saltern crystallizer ponds

To assess, respectively, the contribution of red bacteria of theHalobacterium-Haloferax-Haloarcula group and of the β-carotene-rich green algaDunaliella salina to the red colour of saltern crystallizer ponds, we studied the optical properties of the brines of NaCl-saturated saltern ponds in Eilat, Israel, and quantified the pigments present in their biota. The absorption spectrum of the brines, as measured using the opal glass method to reduce the interference by scattering, or using an integrating sphere, nearly corresponded to thein vivo absorption spectrum of bacterioruberin-containing red archaeobacteria. However, extracts of the microbial community in organic solvents were dominated by β-carotene, a pigment occurring in high concentrations in theDunaliella cells present, and bacterioruberin contributed only between 13 and 28 per cent of the total visible light absorption by the extracts. The apparent discrepancy between these results can be explained by the very small in vivo optical cross-section of β-carotene, which is densely packed in globules inside theD. salina cells.     

On the red coloration of saltern crystallizer ponds. II. Additional evidence for the contribution of halobacterial pigments

In a previous paper we attempted to assess the contribution of red bacteria of theHalobacterium — Haloferax — Haloarcula group and of the -carotene-rich green algaDunaliella salina to the red colour of saltern crystallizer ponds. By means of light absorption measurements, we showed that bacterioruberin contained in the bacteria was mainly responsible for the colour of the brines, in spite of the fact that -carotene derived fromDunaliella was the pigment present in the greatest amount. This apparent discrepancy was explained by the very smallin vivo optical cross-section of -carotene, which is densely packed in globules inside theD. salina cells. We recently observed that the centrifugation technique used in the previous study to collect biomass from the ponds was unsuitable for this type of measurements, as a substantial part of theDunaliella cells present did not sediment upon centrifugation due to the low specific gravity caused by the high -carotene content. Therefore similar measurements were performed with biomass collected by filtration. Again,in vivo absorption spectra were dominated by the absorption peaks of bacterioruberin. The results reported here show that, in spite of the methodological problem associated with the earlier study, all views and conclusions expressed in our earlier paper retain their validity.     

一株菌红素产生菌的鉴定及色素组分分析

对分离自腌鱼的高产菌红素(bacterioruberin)的菌株r-fish进行了形态特征、生理生化特性与细胞化学组分的分析以及基于16SrDNA序列的系统发育分析。形态特征、生理生化特性及细胞化学组分的分析结果表明菌株r-fish为球形的嗜盐古菌。基于16SrDNA序列的系统发育结果表明,r-fish与Halobacterium trapanicum NCIMB784菌株的相似性为99．8％,归入Na-trinema属。用TLC法对r-fish的色素进行了分析,r-fish的色素组分包括菌红素(bacteriorubefin)、脱水菌红素(anhydrobacteriorubefin)、双脱水菌红素(bisanhydrobacteriorubeftn)和一未知色素。与Halobacteriumhalobium和Halococcus morrhuae的色素组分相似。