Crayfish,catfish and snails: the perils of uncontrolled biological control

A recent proposal that the Australian redclaw crayfish Cherax quadricarinatus and hybrid catfish could potentially control the snail hosts of schistosomiasis has been criticised on the grounds that crayfish pose a severe threat to aquatic ecosystems into which it might be introduced. This note examines the issue further, pointing out that both lack the host-specificity requirement to be a successful biological control agent. The catfish Clarias gariepinus is an omnivore and snails form only a small proportion of its diet; there is no evidence to suggest that it controls snail populations anywhere in Africa. The same applies to other species that have been proposed as biological control agents. Simple laboratory experiments are not an adequate guide to the efficiency of an animal as a biological control agent and detailed ecological investigations would usually demonstrate that few African fish species have this capability.     

Protein interaction with ice.

Many organisms have evolved novel mechanisms to minimize freezing injury due to extracellular ice formation. This article reviews our present knowledge on the structure and mode of action of two types of proteins capable of ice interaction. The antifreeze proteins inhibit ice crystal formation and alter ice growth habits. The ice nucleation proteins, on the other hand, provide a proper template to stimulate ice growth. The potential applications of these proteins in different industries are discussed.     

Structure and function of an antifreeze polypeptide from ocean pout, Macrozoarces americanus: role of glutamic acid residues in protein stability and antifreeze activity by site-directed mutagenesis.

The successful expression and purification of the recombinant ocean pout antifreeze polypeptide (rAFP) in Escherichia coli have enabled the study of its structure-function relationship by site-directed mutagenesis. The role of carboxyl groups at Glu23 and Glu36 of the rAFP was probed by replacing these residues with either glutamine or alanine residues as both single and double mutants. The AFP mutants were expressed, purified and characterized in terms of primary and secondary structures, thermal stability and antifreeze activities. The properties of these mutants were compared with those of the rAFP. Three distinct functions are identified for the carboxyl groups: (i) the negative charges at positions 23 and 36 are involved in the thermal stability of the polypeptide; (ii) the negative charges at positions 23 and 36 contribute to the thermal hysteretic activities of the polypeptide; and (iii) the negative charge at position 23 and hydrogen-bonding ability at position 36 contribute to the ice-binding activity of the polypeptide.     

Survival of <Emphasis Type="Italic">Clostridium perfringens</Emphasis>During Simulated Transport and Stability of Some Plasmid-borne Toxin Genes under Aerobic Conditions

Clostridium perfringens is a pathogen of great concern in veterinary medicine, because it causes enteric diseases and different types of toxaemias in domesticated animals. It is important that bacteria in tissue samples, which have been collected in the field, survive and for the classification of C. perfringens into the correct toxin group, it is crucial that plasmid-borne genes are not lost during transportation or in the diagnostic laboratory. The objectives of this study were to investigate the survival of C. perfringens in a simulated transport of field samples and to determine the stability of the plasmid-borne toxin genes cpb1 and etx after storage at room temperature and at 4°C. Stability of the plasmid-borne genes cpb1 and etx of C. perfringens CCUG 2035, and cpb2 from C. perfringens CIP 106526, JF 2255 and 6 field isolates in aerobic atmosphere was also studied. Survival of C. perfringens was similar in all experiments. The cpb1 and etx genes were detected in all isolates from samples stored either at room temperature or at 4°C for 24–44 h. Repeated aerobic treatment of C. perfringens CCUG 2035 and CIP 106526 did not result in the loss of the plasmid-borne genes cpb1, cpb2 or etx. Plasmid-borne genes in C. perfringens were found to be more stable than generally reported. Therefore, C. perfringens toxinotyping by PCR can be performed reliably, as the risk of plasmid loss seems to be a minor problem.