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This work had as main objectives to characterize two bacteriocins produced by lactic acid bacteria (LAB) previously isolated from non-fermented seafood, in order to evaluate their potential as new food protective agents. The two bacteriocinogenic isolates were identified by Polymerase Chain Reaction (PCR) using genus- and species-specific primers, and confirmed by 16S rDNA sequencing, as Enterococcus faecium and Pediococcus pentosaceus. The antimicrobial spectrum of each strain included several indicator microorganisms, some of them also isolated from seafood. Growth of Listeria innocua, L. monocytogenes, Staphylococcus aureus, Bacillus cereus and other LAB species were inhibited, although no inhibition of Gram-negative microorganisms was observed. Proteolytic, but not lipolytic or glycolytic enzymes, completely inactivated the antimicrobial effect of both cell-free supernatants confirming the proteinaceous nature of the inhibitors. The antimicrobial activity was maintained after treatment with NaCl, SDS, Triton X-100, Tween 20, Tween 80 and EDTA after 2 h or 5 h of exposure and both bacteriocins were stable over a wide range of pH and temperatures. Production of bacteriocin by E. faecium (bacALP7) was detected initially at exponential phase and reached a maximum activity of 25,600 AU/ml in the early stationary phase, whereas bacteriocin production by P. pentosaceus ALP57 (bacALP57) reached the maximum at exponential phase with 12,800 AU/ml. The bacteriocins did not kill L. monocytogenes ESB54 nor L. innocua 2030c however, cellular growth was reduced. The partially purified bacteriocins, bacALP7 and bacALP57, were below 6.5 kDa in size as determined by Tricine-SDS gel electrophoresis. E. faecium and P. pentosaceus contained DNA fragments corresponding in size to those recorded for enterocin B and pediocin PA-1, respectively. Sequencing of the fragments from both bacteriocins confirmed the homology. To our knowledge, for the first time two LAB producing bacteriocins similar to pediocin PA-1 and enterocin B, were isolated from non-fermented shellfish. The adaptation of the cultures to seafood matrices may be advantageous in terms of application as a biopreservation strategy for reduction of L. monocytogenes levels in seafood products.

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The thread-like spermatozoon of the crab parasite Microphallus primas was studied by electron microscopy. A survey of the head region of the spermatozoon reveals three features hitherto unknown in Platyhelminthes spermatozoa. The first is the aberrant inclusion of the nucleus within one of the two axonemes, limited to the head end region. The second is the coexistence, in the same axoneme, of two patterns, 9 + 0 (doublets without dynein arms) and 9 + "1". The third is the presence of a layer of cortical microtubules running longitudinally from the zone where the nucleus goes from axoneme to the tail region (where the two flagella start). The sequence of events in spermatogenesis is similar to that described for most of the Digenea trematodes, and the spermiogenesis process conforms to a common plan in nearly the whole group.