Yanqing Duan

Biotransformation of nicotine by microorganism: the case of Pseudomonas spp.

Several bacterial species are capable of using nicotine, the main alkaloid in tobacco plants, as a substrate for growth. The dominant species include members of two genera, Pseudomonas and Arthrobacter. The degradation pathway and genetic structure of nicotine catabolism in Arthrobacter nicotinovorans were recently reviewed (Brandsch Appl Microbiol Biotechnol 69:493–498, 2006). Here, we present up-to-date information on biodegradation of nicotine by Pseudomonas spp. Species in this genus capable of degrading nicotine are summarized and analyzed phylogenetically. Their metabolic intermediates and nicotine degradation-related genes were summarized, and the nicotine-biotransformation pathways were compared and discussed.

Bacterial diversities on unaged and aging flue-cured tobacco leaves estimated by 16S rRNA sequence analysis

Flue-cured tobacco leaves (FCTL) contain abundant bacteria, and these bacteria play very important roles in the tobacco aging process. However, bacterial communities on aging FCTL are not fully understood. In this study, the total microbial genome DNA of unaged and aging flue-cured tobacco K326 were isolated using a culture-independent method, and the bacterial communities were investigated by restriction fragment length polymorphism analysis. Comparison of the number of operational taxonomic units (OTUs) between the cloned libraries from the unaged and aging FCTL showed that the microbial communities between the two groups were different. Fifty and 42 OTUs were obtained from 300 positive clones in unaged and aging FCTL, respectively. Twenty-seven species of bacteria exist in both the unaged and aging FCTL, Bacillus spp. and Pseudomonas spp. were two dominant genera in FCTL. However, 23 bacterial species were only identified from the unaged FCTL, while 15 species were only identified from the aging FCTL. Interestingly, more uncultured bacteria species were found in aging FCTL than in unaged FCTL.

Lysinibacillus tabacifolii sp. nov., a novel endophytic bacterium isolated from Nicotiana tabacum leaves

A Gram-positive, catalase- and oxidase-positive, strictly aerobic, endospore-forming rod bacterium, designated K3514T, was isolated from the leaves of Nicotiana tabacum. The strain was able to grow at temperatures of 8–40°C, pH 5.0–10.0 and NaCl concentrations of 0–7%. The predominant quinones (>30%) of this strain were MK-7(H2) and MK-7. Phylogenetic analysis of 16S rRNA gene sequence showed that strain K3514T was affiliated to the genus Lysinibacillus, with its closest relatives being Lysinibacillus mangiferihumi (98.3% sequence similarity), Lysinibacillus sphaericus (97.9% sequence similarity), Lysinibacillus fusiformis (97.4% sequence similarity), and Lysinibacillus xylanilyticus (97.3% sequence similarity). However, low levels of DNA-DNA relatedness values suggested that the isolate was distinct from the other closest Lysinibacillus species. Additionally, based on analysis of morphological, physiological, and biochemical characteristics, the isolate could be differentiated from the closest known relatives. Therefore, based on polyphasic taxonomic data, the novel isolate likely represents a novel species, for which the name Lysinibacillus tabacifolii sp. nov. and the type strain K3514T (=KCTC 33042T =CCTCC AB 2012050T) are proposed.

Diversity and phylogeny of bacteria on Zimbabwe tobacco leaves estimated by 16S rRNA sequence analysis

Microorganisms play important roles in the tobacco aging process. However, microbial communities on flue-cured tobacco leaves (FCTL) remain largely unknown. In this study, the total microbial genomic DNA of unaged and aging FCTL from Zimbabwe were isolated using a culture-independent method, and the bacterial communities were investigated through analyzing two 16S rRNA gene libraries. Eighty-four and 65 operational taxonomic units were obtained from the libraries of the unaged and aging FCTL, respectively. The following genera were represented more than 4% in both libraries (aging and unaged library): Sphingomonas (4.84%, 4.18%), Stenotrophomonas (4.84%, 5.23%), Erwinia (5.81%, 4.88%), Pantoea (19.35%, 18.47%), and Pseudomonas (21.29%, 24.04%). The dominant species varied between the two libraries. Specifically, several dominant species in unaged FCTL including Pseudomonas fulva, Pseudomonas sp. (AM909658), Klebsiella sp. (HM584796), and Pantoea sp. (AY501386) were not identified in aging FCTL, while several dominant species in aging FCTL such as Pantoea sp. (GU566350), Pseudomonas sp. (EF157292), and Buttiauxella izardii were not found in unaged FCTL. The phylogenetic analysis showed that bacteria from unaged and aging FCTL were divided into two clades, and two unique subclades were identified in aging FCTL. Our results revealed for the first time the bacterial diversities on Zimbabwe tobacco, and provided a basis for clarifying the roles of bacteria in aging process of FCTL.

Two new xanthones from Swertia angustifolia.

Two new xanthones, angustins A and B (1 and 2), were isolated from the aerial parts of Swertia angustifolia together with six known compounds (3–8). The structures of these two xanthones were elucidated by extensive analysis of the spectroscopic data. In addition, compounds 3 and 6–8 were isolated from this plant for the first time.