Most protocols for the preparation of bacterial genomic DNA consist of lysis, followed by incubation with a nonspecific protease and a series of extractions prior to precipitation of the nucleic acids. Such procedures effectively remove contaminating proteins, but are not effective in removing exopolysaccharides which can interfere with the activity of enzymes such as restriction endonucleases and ligases. In this unit, however, the protease incubation is followed by a CTAB extraction whereby CTAB complexes both with polysaccharides and with residual protein, effectively removing both in the subsequent emulsification and extraction. This procedure is effective in producing digestible chromosomal DNA from a variety of gram-negative bacteria, all of which normally produce large amounts of polysaccharides. If large amounts of exceptionally clean DNA are required, the procedure can be scaled up and the DNA purified on a CsCl gradient, as described in the alternate protocol.

Molecular techniques were employed to document the microbial diversity associated with the marine sponge Rhopaloeides odorabile. The phylogenetic affiliation of sponge-associated bacteria was assessed by 16S rRNA sequencing of cloned DNA fragments. Fluorescence in situ hybridization (FISH) was used to confirm the presence of the predominant groups indicated by 16S rDNA analysis. The community structure was extremely diverse with representatives of the Actinobacteria, low-G؉C gram-positive bacteria, the ␤-and ␥-subdivisions of the Proteobacteria, Cytophaga/Flavobacterium, green sulfur bacteria, green nonsulfur bacteria, planctomycetes, and other sequence types with no known close relatives. FISH probes revealed the spatial location of these bacteria within the sponge tissue, in some cases suggesting possible symbiotic functions. The high proportion of 16S rRNA sequences derived from novel actinomycetes is good evidence for the presence of an indigenous marine actinomycete assemblage in R. odorabile. High microbial diversity was inferred from low duplication of clones in a library with 70 representatives. Determining the phylogenetic affiliation of sponge-associated microorganisms by 16S rRNA analysis facilitated the rational selection of culture media and isolation conditions to target specific groups of well-represented bacteria for laboratory culture. Novel media incorporating sponge extracts were used to isolate bacteria not previously recovered from this sponge.

Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are attracted to and then grounded (i.e., forced to land) by lights when they fly at night. We reviewed the current state of knowledge of seabird attraction to light to identify information gaps and propose measures to address the problem. Although species in families such as Alcidae and Anatidae can be grounded by artificial light, the most affected seabirds are petrels and shearwaters (Procellariiformes). At least 56 species of Procellariiformes, more than one-third of them (24) threatened, are subject to grounding by lights. Seabirds grounded by lights have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding grounds confined to formerly uninhabited islands are particularly at risk from light pollution due to tourism and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the most immediate and employed mitigation to reduce the rate of light-induced mortality and save thousands of birds every year. These programs also provide useful information for seabird management. However, these data are typically fragmentary, biased, and uncertain and can lead to inaccurate impact estimates and poor understanding of the phenomenon of seabird attraction to lights. We believe the most urgently needed actions to mitigate and understand light-induced mortality of seabirds are estimation of mortality and effects on populations; determination of threshold light levels and safe distances from light sources; documentation of the fate of rescued birds; improvement of rescue campaigns, particularly in terms of increasing recovery rates and level of care; and research on seabird-friendly lights to reduce attraction.

The complete sequence of the mitochondrial genome of the giant tiger prawn, Penaeus monodon (Arthropoda, Crustacea, Malacostraca), is presented. The gene content and gene order are identical to those observed in Drosophila yakuba. The overall AT composition is lower than that observed in the known insect mitochondrial genomes, but higher than that observed in the other two crustaceans for which complete mitochondrial sequence is available. Analysis of the effect of nucleotide bias on codon composition across the Arthropoda reveals a trend with the crustaceans represented showing the lowest proportion of AT-rich codons in mitochondrial protein genes. Phylogenetic analysis among arthropods using concatenated protein-coding sequences provides further support for the possibility that Crustacea are paraphyletic. Furthermore, in contrast to data from the nuclear gene EF1alpha, the first complete sequence of a malacostracan mitochondrial genome supports the possibility that Malacostraca are more closely related to Insecta than to Branchiopoda.

The T cell receptor (TCR) can interact with a spectrum of peptides as part of its ligand, including the immunogenic peptide, variants of this peptide,and apparently unrelated peptides. The basis of this broad specificity for ligand was investigated by substitution analysis of a peptide antigen and functional testing using a B cell apoptosis assay. A peptide containing as few as 1 aa in common with this peptide could stimulate a specific T cell response. Two endogenous ligands, an agonist and a partial agonist, were readily identified from a search of the SwissProt database, indicating that multiple endogenous ligands likely exist for a given T cell. These findings strongly support the concept that one TCR has the ability to interact productively with multiple different ligands, and provide evidence that such ligands exist in the endogenous peptide repertoire.

No abstract

Rhizobia were isolated from two Kenyan soils with pHs of 4.5 and 6.8 and characterized on the basis of their host ranges for nodulation and nitrogen fixation, colony morphologies, restriction fragment fingerprints, and hybridization with a nifH probe. The populations of rhizobia nodulating Phaseolus vulgaris in the two soils were similar in numbers and in effectiveness of N 2 fixation but were markedly different in composition. The population in the Naivasha soil (pH 6.8) was dominated by isolates specific in host range for nodulation to P. vulgaris; these all had multiple copies, in most cases four, of the structural nitrogenase gene nifH. Only one of the isolates from this soil formed effective nodules on Leucaena leucocephala, and this isolate had only a single copy of nifH. By contrast, the population in the acid Daka-ini soil (pH 4.5) was composed largely of broadhost-range isolates which had single copies of nifH. The isolates from the Daka-ini soil which were specific to P. vulgaris generally had three copies of nifH, although one isolate had only two copies. These rhizobial isolates are indigenous to Kenyan soils and yet have marked similarities to previously described Rhizobium species from other continents.

No abstract