Bacterial communities associated with lesions of two forms of shell disease in the American lobster (Homarus americanus, Milne Edwards) from Atlantic Canada.

Shell disease is a major threat to the American lobster (Homarus americanus, Milne Edwards) fishery. Here we describe the composition of microbial communities associated with lesions of 2 forms of shell disease in Atlantic Canada, (i) a trauma shell disease (TSD) characterized by massive lesions and (ii) an enzootic shell disease (EnSD) characterized by irregularly shaped lesions with a distinct orange to yellow color. The microbiology of the lesions was described by polymerase chain reaction and denaturing gradient gel electrophoresis of 16S rDNA amplified from scrapings of the shell lesions and was compared with communities of unaffected carapaces and previously described forms of shell diseases. Both TSD and EnSD lesions were dominated by members of Alphaproteobacteria, Gammaproteobacteria, and Flavobacteria, all commonly detected in other forms of shell disease; however, unique members of Epsilonproteobacteria were also present. Two Vibrio spp. and 2 Pseudoalteromonas spp. were dominant in lesions of TSD and a Tenacibaculum sp. and Tenacibaculum ovolyticum were dominant in lesions of EnSD. The TSD and EnSD in this study contained similar taxa as other shell disease forms; however, their microbiology is mostly different and neither resembles that of epizootic shell disease.

Isolation and partial characterisation of four novel plasma lectins from the American lobster Homarus americanus.

Although numerous haemolymph-derived crustacean lectins are described, few have been reported for the American lobster Homarus americanus. In the present study, affinity chromatography was used to isolate and partially describe the carbohydrate affinity of four new lectins from H. americanus plasma. HaMBP and HaDNABP were homodimers of approximately 30 kDa subunits which bound to mannan- and DNA-agarose columns, respectively. These proteins had partially overlapping elution profiles, and both shared and unique amino acid sequences and fragmentation patterns after trypsin digestion. A third homodimer of approximately 29 kDa subunits eluted with HaMBP and HaDNABP under certain conditions. HaNBP occurred as a monomer and dimer of approximately 40 kDa subunits and was recovered in relatively large quantities from mannan-agarose with N-acetylated sugars. Transmission electron microscopy revealed HaNBP to be a linear protein composed of multiple globular subunits.

A 2.13 A structure of E. coli dihydrofolate reductase bound to a novel competitive inhibitor reveals a new binding surface involving the M20 loop region.

Dihydrofolate reductase (DHFR) is a vital metabolic enzyme and thus a clinically prominent target in the design of antimetabolites. In this work, we identify 1,4-bis-{[N-(1-imino-1-guanidino-methyl)]sulfanylmethyl}-3,6-dimethyl-benzene (compound 1) as the correct structure of the previously reported DHFR inhibitor 1,4-bis-{(iminothioureidomethyl)aminomethyl}-3,6-dimethyl-benzene (compound 2). The fact that compound 1 has an uncharacteristic structure for DHFR inhibitors, and an affinity (KI of 11.5 nM) comparable to potent inhibitors such as methotrexate and trimethoprim, made this inhibitor of interest for further analysis. We have conducted a characterization of the primary interactions of compound 1 and DHFR using a combination of X-ray structure and SAR analysis. The crystal structure of E. coli DHFR in complex with compound 1 and NADPH reveals that one portion of this inhibitor exploits a unique binding surface, the M20 loop. The importance of this interface was further confirmed by SAR analysis and additional structural characterization.