Spatial and temporal patterns of distribution and abundance of a tropical fish assemblage in a seasonal Sargassum bed, Cabo Frio Island, Brazil

The patterns of distribution and abundance of a fish community were influenced by the magnitude of the canopy of Sargassum furcatum . It is suggested that the fish community in the sublittoral of Farol Beach is structured mainly by factors related to the availability of space and habitats. Quantitative data were collected by visual census techniques, along a belt of 30X2 m in each habitat. Fish diversity was greater in S. furcatum bed and in the rocks, than in the sand where there is less structural complexity. The fish density was related to the macroalgal biomass. Correspondence analysis and cluster analysis were used to describe and compare fish assemblages in three different habitats. The association observed between the juveniles of the sparid Diplodus argenteus , the grunt Haemulon aurolineatum and the surgeonfish Acanthurus bahianus and the different habitats in the summer, and juveniles of the other species in the autumn, indicates a pattern of recruitment of the species in these periods.     

Conformation of the peptide antibiotic – histatin 8 in aqueous and non aqueous media

Summary Histatin 8 (Lys¹-Phe-His-Glu-Lys⁵-His-His-Ser-His-Arg¹⁰-Gly-Tyr¹²) belongs to a group of related neutral and basic histidine rich peptides present in human salivary secretions that possess fungicidal and bactericidal activities. The conformation of this peptide has been examined by¹H and¹³C 2D-NMR in DMSO-d₆, water (pH 4.0) and 40% HFA solutions. MD simulations incorporating NMR data was used to generate the solution conformations. The structures were refined byMARDIGRAS employing theRANDMARDI approach. In both DMSO-d₆ and water, the peptide is seen to adopt a β-pleated sheet, while HFA induces an α-helix structure. The role of these structures in its mechanism of action has been explained. This article was presented at the Astra-Zeneca International Symposium on Progress in Drug Discovery and Development Sciences, Bangalore, India, 17–19 January 2001.     

Isolation of Enterobacter cowanii from Eucalyptus showing symptoms of bacterial blight and dieback in Uruguay

Aims:  This study was performed to identify bacterial strains isolated simultaneously with Pantoea species from Eucalyptus trees showing symptoms of bacterial blight and dieback in Uruguay.
Methods and Results:  Several molecular techniques including 16S rRNA and rpoB gene sequencing and DNA–DNA hybridization were used to characterize the Gram-negative, facultatively anaerobic, slime-producing bacterial strains isolated along with Pantoea species from Eucalyptus . Hypersensitivity reactions (HR) and pathogenicity tests were performed on tobacco and Eucalyptus seedlings, respectively. The isolates clustered closely with the type strain of Enterobacter cowanii in both phylogenetic trees constructed. The DNA–DNA similarity between the isolates and the type strain of Ent. cowanii ranged from 88% to 92%. A positive HR was observed on the tobacco seedlings, but no disease symptoms were visible on the inoculated Eucalyptus seedlings.
Conclusions:  Enterobacter cowanii was isolated from trees with symptoms of bacterial blight although strains of this bacterial species do not appear to be the causal agent of the disease.
Significance and Impact of the Study:  This study provides the first report of Ent. cowanii isolated from Eucalyptus . Its presence in Eucalyptus tissue suggests that it is an endophyte in trees showing symptoms of blight.     

Evolution of the Genes Encoding Seed Storage Proteins in Sugarcane and Maize

Prolamins, the seed storage proteins of maize, sorghum and coix were also found in sugarcane. Prolamins are grouped into structurally distinct classes termed the α-, β-, γ- and δ-prolamins. Orthologues for almost all of the α-, β-, γ- and δ-prolamins classes were identified in sugarcane. In maize, there are two molecular weight classes of α-prolamins, the 22 and 19 kD α-zeins. Sugarcane also possesses both the 22 kD and the 19 kD α-prolamins, which we denote as caneins, whereas sorghum and coix contain only the 22 kD α-prolamin (α-kafirin and α-coixin, respectively). Amino acid sequence alignments of the 22 and 19 kD α-prolamins from these plants revealed that both the 19 kD α-zein and the 19 kD α-canein lack around 20 amino acids at the sixth α-helix domain. We postulate that the 19 kD α-prolamins originated from a deletion of the sixth α-helix of a 22 kD counterpart in the saccharum lineage. Saccharum and sorghum diverged around five to nine million years ago (Mya), when only the 22 kD α-prolamins existed. The 19 kD α-canein must therefore have emerged after this time. Sorghum possesses a 19 kD α-prolamin similar to that of sugarcane and maize, but it contains the sixth α-helix domain lacking in the 19 kD α-zein and the 19 kD α-canein. This sorghum α-prolamin that we called 19 kD-like α-kafirin must be the ancestor of the 19 kD α-canein. The 19 kD-like α-kafirin could also be the ancestor of the 19 kD α-zein but it is also possible that the genes encoding the 19 kD α-zein and the 19 kD α-canein have evolved separately in these close groups.     

High frequency of natural autoantibodies in normal newborn mice

Spleen cells from 6-day-old nonimmunized BALB/c and BALB.B10 mice were fused with the nonsecreting hybridoma cell line Sp2/0. Three hundred and eighty-four immunoglobulin-secreting hybrids were screened for antibody activity against mouse actin, tubulin, and myosin, and against TNP, peroxidase, renin, DNA, and neurofilaments. At least 24 hybridomas in the collection (6.25%) exhibited antibody activity against this panel of antigens. Ten of these hybrids were cloned, were propagated, and the corresponding monoclonal IgM protein was isolated from ascitic fluids and was further characterized. At least four groups of antibody specificities were identified: 1) one clone reacting with TNP only; 2) one clone reacting with both actin and tubulin; 3) two clones which bound to both TNP and actin; and 4) a fourth group, comprising the six other clones, which all exhibited widespread reactivity and bound to actin, tubulin, myosin, and TNP. These results indicate: 1) B cell clones directed against self antigens are activated in the internal environment and are recovered consequently by somatic cell hybridization; 2) the widespread antibody specificities found for these newborn mouse antibodies are very similar to those previously characterized with human natural antibodies and human monoclonal Ig; and 3) the frequency of B cells binding to cytoskeletal proteins and TNP is very high (at least 6.25%).