D70847), and Rba. azotoformans S3 (GenBank accession no. DQ402051). Based on these results, CGMCC 6086 was identified as Rba. azotoformans. Two DNA fragments containing carotenogenesis genes were amplified via PCR from the genomic DNA of Rba. azotoformans CGMCC 6086. The GenBank accession number was JF723980. A 4.9 kb fragment containing four carotenogenesis genes (crtA, crtI,

crtB, and tspO) was amplified with primers Ra-Ad and Ra-Od (Table 1). The other 5.3 kb fragment containing four carotenogenesis genes (crtC, crtD, crtE, see more and crtF) was amplified with primers Ra-Fd and Ra-Cd (Table 1). The putative gene products showed a higher identity to their counterparts in Rba. sphaeroides (83–97%) than in Rba. capsulatus (48–68%), Rvi. gelatinosus (33–53%), and Rhodopseudomonas palustris (42–53%) by protein-to-protein alignment Selleck BMN 673 (Table S2). The neighboring genes on both sides of the crtAIB-tspO fragment were bchI and the ferredoxin gene. Those on both sides of the crtCDEF fragment were the dihydrodipicolinate synthase gene and bchC (Fig. 2). According to the acquired sequence of carotenogenesis gene cluster from Rba. azotoformans CGMCC 6086 (GenBank

accession no. JF723980), four primers (Ra-Af, Ra-Of, Ra-Ff, and Ra-Cf) were designed to amplify the sequence between the crtAIB-tspO and crtCDEF fragments. However, no fragments could be amplified by those primers. The result meant that the eight carotenogenesis genes were located in two separate regions within the genome and were clustered DOK2 as crtAIB-tspO and crtCDEF. Several organizations of the carotenogenesis gene cluster in purple photosynthetic bacteria have been reported (Fig. 2). In Rba. sphaeroides and Rba. capsulatus, eight carotenogenesis genes were successively clustered in the sequence crtAIB-tspO-crtCDEF (Armstrong et al., 1989; Lang et al., 1995). In Rvi. gelatinosus, seven carotenogenesis genes are separated into three parts (crtBCDA, crtFE, and crtI fragments) by genes involved in the biosynthesis of bacteriochlorophyll and photosynthetic

reaction center (Igarashi et al., 2001). In Tca. roseopersicina, a partial carotenogenesis gene cluster has been cloned. A crtCDEF fragment and a separated crtI gene were determined (Kovacs et al., 2003). In Rps. palustris, the crtBCDA and crtFE fragments were separated by a 21.9 kb fragment containing genes involved in phosphonate metabolism (Larimer et al., 2004). In Rhodospirillum rubrum, the crtBCDA and crtFE fragments are widely dispersed in the chromosome (Reslewic et al., 2005). In this study, the eight carotenogenesis genes from Rba. azotoformans CGMCC 6086 were located in two separate regions, although each region had the same gene order as that of Rba. sphaeroides and Rba. capsulatus. The genes located downstream of tspO and crtC were not involved in the photosynthetic gene cluster. The organization of the carotenogenesis gene cluster was unusual for purple photosynthetic bacteria.