Biosurfactants from thermophilic dairy streptococci and their potential role in the fouling control of heat exchanger plates

Recent work on biosurfactant release by thermophilic dairy streptococci is reviewed. There is a suggestion thatStreptococcus thermophilus isolates may release biosurfactants that stimulate detachment of already-adhering cells and leave an anti-adhesive coating on a substratum. A previously published rapid screening method is described for the identification of biosurfactant-releasing microorganisms, and growth medium supplements to enhance biosurfactant release by thermophilic dairy streptococci are reported. New experimental work described includes the isolation and purification of biosurfactants from dairy isolates by thin layer chromatography. Many compounds isolated were extremely surface-active and reduced the water surface tension to values around 30 mJ m^–2 at a concentration of 10 mg ml^–1. Most importantly, the thin layer chromatograms of various isolates resembled each other, and an adsorbed purified compound from one isolate retarded the deposition to glass of another isolate by a factor of two. Provided our findings implicate that these biosurfactants could also be adsorbed to heat exchanger plates in pasteurizers and thereby retard colonization by thermophilic streptococci, these compounds may have major economic implications. Further work is required, however.     

Initial steps towards a production platform for DNA sequence analysis on the grid

Background  

Bioinformatics is confronted with a new data explosion due to the availability of high throughput DNA sequencers. Data storage and analysis becomes a problem on local servers, and therefore it is needed to switch to other IT infrastructures. Grid and workflow technology can help to handle the data more efficiently, as well as facilitate collaborations. However, interfaces to grids are often unfriendly to novice users.     

Inactivation of <Emphasis Type="Italic">Dicer1</Emphasis> in Steroidogenic factor 1-positive cells reveals tissue-specific requirement for <Emphasis Type="Italic">Dicer1</Emphasis>in adrenal,testis, and ovary

Background  

The synthesis of microRNA (miRNA) is a multi-step process that requires the action of the ribonuclease Dicer1. Dicer1 is responsible for the final processing of miRNA and has been implicated in cellular processes such as proliferation, apoptosis, and differentiation. Mouse embryos lacking Dicer1 die in early embryogenesis. In this study, we investigated whether Dicer1 is required for development of adrenal, testis, and ovary in mouse embryos.     

Transient association of MCM complex proteins with the nuclear matrix during initiation of mammalian DNA replication

The minichromosome maintenance complex (MCM2-7) is the putative DNA helicase in eukaryotes, and essential for DNA replication. By applying serial extractions to mammalian cells synchronized by release from quiescence, we reveal dynamic changes to the sub-nuclear compartmentalization of MCM2 as cells pass through late G1 and early S phase, identifying a brief window when MCM2 becomes transiently attached to the nuclear-matrix. The data distinguish 3 states that correspond to loose association with chromatin prior to DNA replication, transient highly stable binding to the nuclear-matrix coincident with initiation, and a post-initiation phase when MCM2 remains tightly associated with chromatin but not the nuclear-matrix. The data suggests that functional MCM complex loading takes place at the nuclear-matrix.     

Lateral wall protein content mediates alterations in cochlear outer hair cell mechanics before and after hearing onset

Specialized outer hair cells (OHCs) housed within the mammalian cochlea exhibit active, nonlinear, mechanical responses to auditory stimulation termed electromotility. The extraordinary frequency resolution capacity of the cochlea requires an exquisitely equilibrated mechanical system of sensory and supporting cells. OHC electromotile length change, stiffness, and force generation are responsible for a 100-fold increase in hearing sensitivity by augmenting vibrational input to non-motile sensory inner hair cells. Characterization of OHC mechanics is crucial for understanding and ultimately preventing permanent functional deficits due to overstimulation or as a consequence of various cochlear pathologies. The OHCs' major structural assembly is a highly-specialized lateral wall. The lateral wall consists of three structures; a plasma membrane highly-enriched with the motor-protein prestin, an actin-spectrin cortical lattice, and one or more layers of subsurface cisternae. Technical difficulties in independently manipulating each lateral wall constituent have constrained previous attempts to analyze the determinants of OHCs' mechanical properties. Temporal separations in the accumulation of each lateral wall constituent during postnatal development permit associations between lateral wall structure and OHC mechanics. We compared developing and adult gerbil OHC axial stiffness using calibrated glass fibers. Alterations in each lateral wall component and OHC stiffness were correlated as a function of age. Reduced F-actin labeling was correlated with reduced OHC stiffness before hearing onset. Prestin incorporation into the PM was correlated with increased OHC stiffness at hearing onset. Our data indicate lateral wall F-actin and prestin are the primary determinants of OHC mechanical properties before and after hearing onset, respectively.     

Differential synthesis of β-tubulin isotypes in gerbil nasal epithelia

Compartmentalization of beta-tubulin isotypes within cells according to function was examined in gerbil olfactory and respiratory epithelia by using specific antibodies to four beta-tubulin isotypes (beta(I), beta(II), beta(III), and beta(IV)). Isotype synthesis was cell-type-specific, but the localization of the isotypes was not compartmentalized. All four isotypes were found in the cilia, dendrites, somata, and axons of olfactory neurons. Only two isotypes (beta(I) and beta(IV)) were present in the cilia of nasal respiratory epithelial cells. The beta(IV) isotype, thought to be an essential component of cilia, was present in olfactory neurons and respiratory epithelial cells, which are ciliated, but was not found in basal cells (the stem cells of olfactory sensory neurons, which have no cilia). Olfactory neurons therefore do not synthesize beta(IV)-tubulin until they mature, when functioning cilia are also elaborated. The failure to observe compartmentalization of beta-tubulin isotypes in olfactory neurons sheds new light on potential functions of the beta-tubulin isotypes.