The Genus Isolaimium Cobb, 1920 (Order Isolaimida,Isolaimiidae New Family)

Five species of lsolaimium Cobb, 1920 are described and illustrated: I. nigeriense n. sp., I. multipapillatum n. sp., I. caliIornicum, n. sp., I. papillatum Cobb, 1920, and I stictochroum Timm, 1961. A unique feature in lsolaimium, not found in any other nematode, is the presence of six cuticularized tubes surrounding the stoma and opening on the head. Order Isolaimida Cobb, 1920 is emended to accommodate this genus, which is considered to lie between the mermithoids and the dorylaimoids.     

Effects of competition and shading in planktonic communities

A model for several algal species which compete both for light and for nutrients, and which are also subject to settling and diffusion, is considered. The settling speeds and diffusion coefficients are assumed to be small, in a sense to be made precise later, and a singular perturbation argument is used. In certain cases vertical segregation of the algal species is observed, and the mechanism for this is interpreted biologically.Supported by the Danish Natural Science Research Council (Grant No. 11-8321)     

Biodegradation of sulfamethoxazole by a bacterial consortium of Achromobacter denitrificans PR1 and Leucobacter sp. GP

In the last decade, biological degradation and mineralization of antibiotics have been increasingly reported feats of environmental bacteria. The most extensively described example is that of sulfonamides that can be degraded by several members of Actinobacteria and Proteobacteria. Previously, we reported sulfamethoxazole (SMX) degradation and partial mineralization by Achromobacter denitrificans strain PR1, isolated from activated sludge. However, further studies revealed an apparent instability of this metabolic trait in this strain. Here, we investigated this instability and describe the finding of a low-abundance and slow-growing actinobacterium, thriving only in co-culture with strain PR1. This organism, named GP, shared highest 16S rRNA gene sequence similarity (94.6–96.9%) with the type strains of validly described species of the genus Leucobacter. This microbial consortium was found to harbor a homolog to the sulfonamide monooxygenase gene (sadA) also found in other sulfonamide-degrading bacteria. This gene is overexpressed in the presence of the antibiotic, and evidence suggests that it codes for a group D flavin monooxygenase responsible for the ipso-hydroxylation of SMX. Additional side reactions were also detected comprising an NIH shift and a Baeyer–Villiger rearrangement, which indicate an inefficient biological transformation of these antibiotics in the environment. This work contributes to further our knowledge in the degradation of this ubiquitous micropollutant by environmental bacteria.

     

Tetra-acetylenic metabolites from Mycena viridimarginata

The structures of two new acetylenic compounds from Mycena viridimarginata were elucidated by spectroscopic methods and some chemical transformations. The major metabolite was 10-hydroxyundeca-2,4,6,8-tetraynamide and the minor one was 3,4,13-trihydroxytetradeca-5,7,9,11-tetraynoic acid γ-lactone. Another compound, methyl-3,4,13-trihydroxytetradeca-5,7,9,11-tetraynoate, was found to be an artifact from the γ-lactone produced on the Sephadex LH-20 column. Furthermore, model compounds were prepared to establish the chromophoric system of the major metabolite.