The kinetics of cell wall turnover in Bacillus subtilis have been examined in detail. After pulse labeling of the peptidoglycan with N-acetylglucosamine, the newly formed peptidoglycan is stable for approximately three-quarters of a generation and is then degraded by a process that follows first-order kinetics. Deprivation ofan auxotroph ofamino acids required for protein synthesis results in a cessation of turnover. If a period of amino acid starvation occurs during the lag phase of turnover, then the initiation of turnover is delayed for a period of time equivalent to the starvation period. During amino acid starvation, new cell wall peptidoglycan is synthesized and added to preexisting cell wall. This peptidoglycan after resumption of growth is also subject to degradation (turnover). It is suggested that cell wall turnover is dependent on cell growth and elongation. Several possible control mechanisms for cell wall autolytic enzymes are discussed in light of these observations.The cell wall peptidoglycan of many grampositive microorganisms turns over during logarithmic growth (3-6, 11, 12, 21, 22, 26, 27, 31). A number of observations suggest that peptidoglycan turnover is not required for normal cell growth (13); however, the phenomenon is of interest because it may provide clues to the mode of cell wall growth and assembly and some insight into the regulation of cell wall autolytic enzymes.Previous work with Bacillus subtilis has shown that after pulse labeling of the peptidoglycan, there is a lag period, equivalent in time to 0.5 to 1.0 generations, during which the newly synthesized peptidoglycan is immune from turnover. After this lag period, the peptidoglycan is degraded by a process that follows first-order kinetics, and the products ofpeptidoglycan turnover (glycan strands and peptide bridges) appear in the growth medium (21). If any fraction of the peptidoglycan in this organism is resistant to turnover, it must represent less than 5% of the total cell wall (12,21). Although the loss of radioactivity from the cell wall is about 50% per generation, it has been pointed out by Pooley (26,27) that since there is a lag between the time at which peptidoglycan is synthesized and the time at which it is degraded, the loss ofpeptidoglycan from the cell is only 10 to 20% of the mass of the cell wall per generation.Cell wall turnover has also been demonstrated in a variety of other gram-positive organisms including Streptococcus aureus (31), Lac-tobacillus acidophilus (3,11), and B. megaterium (4-6, 21), each of which shows somewhat different kinetic characteristics than the turnover observed with B. subtilis.In this communication we have examined some of the kinetics of cell wall turnover in B. subtilis, and its relation to cell growth. The results appear to place important restrictions on any model of cell wall expansion in this organism. MATERIALS AND METHODSThe bacterial strains used were either the Marburg strain of B. subtilis (ATCC 6051) or a derivative of this strain, B. subtilis B42, kindly made availab...

A survey of PDE4 inhibitors reveals that some compounds trigger intracellular aggregation of PDE4A4 into accretion foci through association with the ubiquitin-binding scaffold protein p62 (SQSTM1). We show that this effect is driven by inhibitor occupancy of the catalytic pocket and stabilization of a "capped state" in which a sequence within the enzyme's upstream conserved region 2 (UCR2) module folds across the catalytic pocket. Only certain inhibitors cause PDE4A4 foci formation, and the structural features responsible for driving the process are defined. Switching to the UCR2-capped state induces conformational transition in the enzyme's regulatory N-terminal portion, facilitating protein association events responsible for reversible aggregate assembly. PDE4-selective inhibitors able to trigger relocalization of PDE4A4 into foci can therefore be expected to exert actions on cells that extend beyond simple inhibition of PDE4 catalytic activity and that may arise from reconfiguring the enzyme's protein association partnerships.

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The N-acetylmuramic acid L-alanine amidase from Bacillus subtilis W-23 has been purified to apparent homogeneity. The enzyme is a monomer of molecular weight 51,000, which binds extremely tightly to homologous cell walls but not to heterologous cell walls, even of the closely related strain B. subtilis ATCC 6051. This difference in binding is only in part due to differences in teichoic acid between these two strains and to a large extent appears to represent differences in the arrangement of the peptidoglycan. A comparison of the amidase from B. subtilis W-23 and the enzyme previously purified from B. subtilis ATCC 6051 (Herbold and Glaser, 1975) shows that the two proteins, which cleave the same bond and are of the same size, do not cross-react immunologically and that the two enzymes are, therefore, not closely related in structure. Recent work in this laboratory has shown that the N-acetylmuramic acid L-alanine amidase from Bacillus subtilis ATCC 6051 uses teichoic acid as an allosteric ligand (11, 12), which is responsible for the very tight binding of the enzyme to the cell wall. It was also shown that the cells contain a protein activator of the enzyme which, when combined with the enzyme, results in processive cleavage of the cell wall only if the cell wall contains the homologous teichoic acid. B. subtilis W-23 has a cell wall structure very similar to that ofB. subtilis ATCC 6051 (14) but differs from it'in that B. subtilis W-23 has a ribitol teichoic acid (5) whereas B. subtilis ATCC 6051 has glycerol teichoic acid (9). Initial observations with a crude N-acetylmuramic acid L-alanine amidase from B. subtilis W-23 suggested that it used polyribitol phosphate as an allosteric ligand (12). It seemed desirable to

In its first national strategy on dementia, the Government of Canada has highlighted the need to improve quality of care for individuals living with dementia, with emphasis on following best practices and evidence in care delivery and providing care staff access to education and training. It is also known that the design of the physical environment of care homes is integral to the care experience of individuals living with dementia. Therefore, this study aims to identify the best national and international practices implemented in care homes for people living with dementia in: (1) education, training, staffing, and care practices; and (2) environmental design and physical infrastructure, through the review of relevant grey literature. This article highlights key recommendations for improving the quality of care for residents living with dementia in care homes, such as: (1) facilitating translation of training into practice, (2) maintaining consistent staffing levels, and (3) designing care homes to facilitate wayfinding, accessibility, safety, comfort, appropriate sensory stimulation, familiarity, and homelikeness. The findings from this review are expected to inform the development of guidelines for a provincial dementia-friendly care home designation program and various advocacy efforts to help achieve the objectives of the national strategy on dementia.