Contamination of food by Listeria monocytogenes is thought to occur most frequently in food-processing environments where cells persist due to their ability to attach to stainless steel and other surfaces. Once attached these cells may produce multicellular biofilms that are resistant to disinfection and from which cells can become detached and contaminate food products. Because there is a correlation between virulence and serotype (and thus phylogenetic division) of L. monocytogenes, it is important to determine if there is a link between biofilm formation and disease incidence for L. monocytogenes. Eighty L. monocytogenes isolates were screened for biofilm formation to determine if there is a robust relationship between biofilm formation, phylogenic division, and persistence in the environment. Statistically significant differences were detected between phylogenetic divisions. Increased biofilm formation was observed in Division II strains (serotypes 1/2a and 1/2c), which are not normally associated with food-borne outbreaks. Differences in biofilm formation were also detected between persistent and nonpersistent strains isolated from bulk milk samples, with persistent strains showing increased biofilm formation relative to nonpersistent strains. There were no significant differences detected among serotypes. Exopolysaccharide production correlated with cell adherence for highbiofilm-producing strains. Scanning electron microscopy showed that a high-biofilm-forming strain produced a dense, three-dimensional structure, whereas a low-biofilm-forming strain produced a thin, patchy biofilm. These data are consistent with data on persistent strains forming biofilms but do not support a consistent relationship between enhanced biofilm formation and disease incidence.

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Abstract-Developmental changes in contractile behavior are known to occur during fetal and postnatal heart development.In this study, we examined whether adaptations take place in titin. A range of species was used to evaluate titin isoform expression and altered function during cardiac muscle development. A novel titin exon microarray that allows all 363 titin exons to be monitored simultaneously was used for transcript studies. Results reveal expression of fetal titin isoforms, characterized by additional spring elements both in the tandem Ig and PEVK region of the molecule. At the protein level, the fetal cardiac isoform predominates in fetal and neonatal myocardium and gradually disappears during postnatal development with a time course that varies in different species. Passive myocardium, contrary to previous reports, was found to be less stiff in the neonate than in the adult. This can be explained by the unique spring composition of fetal cardiac titin expressed by the neonate. Changes in titin expression are likely to impact functional transitions and diastolic filling behavior during development of the heart. (Circ Res. 2004;94:505-513.)Key Words: diastole Ⅲ compliance Ⅲ filling Ⅲ connectin Ⅲ microarray L arge changes in hemodynamic load occur during the course of cardiac development and are known to be associated with changes in contractility due to alterations in isoform expression patterns of sarcomeric proteins. 1,2 Whether changes occur in passive tension of the myocardium is less well established. Research performed decades ago revealed that passive stiffness is highest in fetal myocardium and progressively decreases with age. 3,4 To our knowledge, this earlier work has not been followed up. Furthermore, the molecular basis of the adaptations in passive stiffness during cardiac development is also unknown, except that the total amount of collagen in fetal and adult myocardium appears unaltered. 5 Considering that titin is a major source of passive stiffness in adult myocardium, 6,7 we investigated titin's role in the developmental regulation of passive stiffness.Titin is a giant protein that spans the half sarcomere with an I-band segment that functions as a molecular spring, the elastic properties of which define the passive mechanical properties of the cardiac myocyte. 8 Titin is encoded by a single gene containing in humans 363 exons that are differentially spliced in the adult heart, creating the stiff N2B (short molecular spring) and more compliant N2BA (long molecular spring) isoforms. 9,10 These isoforms can be coexpressed in the same sarcomere, allowing passive stiffness to be adjusted anywhere in-between that of stiff sarcomeres that express only N2B titin and compliant sarcomeres that express N2BA titin. 11 Recent work revealed that differential splicing is subject to regulatory mechanisms that control entry to either N2B or N2BA splice-pathways. 7,12,13 For example, the adult canine myocardium coexpresses N2B and N2BA titins at a similar level, but in response to long-term tachy...

We report on the development and validation of a simple microarray method for the direct detection of intact 16S rRNA from unpurified soil extracts. Total RNAs from Geobacter chapellei and Desulfovibrio desulfuricans were hybridized to an oligonucleotide array consisting of universal and species-specific 16S rRNA probes. PCRamplified products from Geobacter and Desulfovibrio were easily and specifically detected under a range of hybridization times, temperatures, and buffers. However, reproducible, specific hybridization and detection of intact rRNA could be accomplished only by using a chaperone-detector probe strategy. With this knowledge, assay conditions were developed for rRNA detection using a 2-h hybridization time at room temperature. Hybridization specificity and signal intensity were enhanced using fragmented RNA. Formamide was required in the hybridization buffer in order to achieve species-specific detection of intact rRNA. With the chaperone detection strategy, we were able to specifically hybridize and detect G. chapellei 16S rRNA directly from a total-RNA soil extract, without further purification or removal of soluble soil constituents. The detection sensitivity for G. chapellei 16S rRNA in soil extracts was at least 0.5 g of total RNA, representing approximately 7.5 ؋ 10 6