Arthropod Diversity in Rice nurseries in North-Eastern Zone of Tamil Nadu

Agricultural systems are often considered by ecologists as disturbed, depauperate, and evolutionarily recent. But tropical rice agro-ecosystem is one exception due to its ecological complexity resulted by the long ecological complexity resulted by the long ecological history and wide geographical distribution. Rice nursery is very similar to natural grassland and offers a wide scope for studying the biodiversity due to the presence of arthropod fauna. A survey was conducted in five rice nursery fields in the same period in three villages of two districts of the north eastern zone of Tamil Nadu: Budur, Kavarapettai and Narasingapuram of Tiruvallur district, and Kavur and Malaiyambakkam of Kancheepuram district during Sornavari season,2003(April to August). The rice cultivar was uniformly ADT 43, a short duration variety. No chemical pesticide was applied in the nursery fields and the seedlings were of uniform age. Fifty double sweep net samples were taken to study arthropod diversity. The specimens sorted out were grouped into three guilds, viz., pests, entomophages and neutrals, and their relative abundance was worked out. . The overall observations revealed that a wide range of arthropod fauna were present in the rice nursery fields. The neutrals were the most dominant guilds in four out of five locations. The relative abundance range from 30.22 to 67.13% .This guild was followed by the pests, which ranged from 17.5 to 48.58%. The abundance of entomophages ranged from 13.32 to 24.36%. Among the locations, the maximum relative abundance of pest and entomophage guilds was observed in Narasingapuram. The maximum relative abundance of neutrals was observed in Budur. The green leaf hopper, white flies, white-bat plant hopper, grass hoppers and trips were the major pests. The pre dominant entomophages were the spiders, parasitic hymenoptera and ground beetles. Dipteran flies and hydrophilids were the pre dominant neutrals observed. It may be concluded that rice nursery field supports a wide range of arthropods. The neutrals help in the buildup of carnivorous (entomophages), which ultimately check the pest population

Lactobacillus reuteri DSM 20016 Produces Cobalamin-Dependent Diol Dehydratase in Metabolosomes and Metabolizes 1,2-Propanediol by Disproportionation▿

A Lactobacillus reuteri strain isolated from sourdough is known to produce the vitamin cobalamin. The organism requires this for glycerol cofermentation by a cobalamin-dependent enzyme, usually termed glycerol dehydratase, in the synthesis of the antimicrobial substance reuterin. We show that the cobalamin-synthesizing capacity of another L. reuteri strain (20016, the type strain, isolated from the human gut and recently sequenced as F275) is genetically and phenotypically linked, as in the Enterobacteriaceae, to the production of a cobalamin-dependent enzyme which is associated with a bacterial microcompartment (metabolosome) and known as diol dehydratase. We show that this enzyme allows L. reuteri to carry out a disproportionation reaction converting 1,2-propanediol to propionate and propanol. The wide distribution of this operon suggests that it is adapted to horizontal transmission between bacteria. However, there are significant genetic and phenotypic differences between the Lactobacillus background and the Enterobacteriaceae. Electron microscopy reveals that the bacterial microcompartment in L. reuteri occupies a smaller percentage of the cytoplasm than in gram-negative bacteria. DNA sequence data show evidence of a regulatory control mechanism different from that in gram-negative bacteria, with the presence of a catabolite-responsive element (CRE) sequence immediately upstream of the pdu operon encoding diol dehydratase and metabolosome structural genes in L. reuteri. The metabolosome-associated diol dehydratase we describe is the only candidate glycerol dehydratase present on inspection of the L. reuteri F275 genome sequence