No abstract

A dsor#tion at Inorganic Szcr faces. Part I .held water. The film formed in chromic acid is the purest and is almost entirely y-alumina (s.g. ca. 2-7) with only ca. 0-1% of impurity (as Cr). Some partial hydration of the oxide may take place during electrolysis but the present work gives no evidence of this. The degree of crystallinity appears to increase with rise in temperature of the electrolyte. Dry heating above 100" drives off any loosely held water, but does not decrease the adsorptive powers; treatment with steam or with water above W", however, causes the f i l m to lose its adsorptive powers entirely. This effect, known as " sealing," is caused by blocking of the pores through the formation of a thin layer of a-alumina monohydrate (boehmite) containing an additional molecule of lattice water. Dry heating above 100" subsequent to sealing removes water and reconverts a proportion of the monohydrate into y-alumina. The adsorptive capacity of the film is thus partially restored. Heating to temperatures up to 650" does not appreciably alter the film, but at ca. 900" the internal structure changes entirely, and a-alumina is produced (

No abstract

Quantitative adsorption tests with aromatic solutes (mainly sulphonated dyes) and chromic acid anodic alumina film are described. The adsorption mechanism of the non‐chelating dyes is probably covalent bond formation (each sulphonate group replacing a hydroxy‐group or a chromate group attached to aluminium), together with some ion‐exchange adsorption of anionic micelles. Chelating dyes form an aluminium chelate‐complex with the film. The sequence of events in adsorption from water appears to be: (i) film etching rapid dissolution (<5 min.) of a surface layer of alumina, (ii) rapid adsorption of an external layer of solute, (iii) slow inward diffusion of solute from the external layer to complete a monolayer, (iv) (with sulphonates) penetration (and ultimate breakdown) of the oxide crystal structure, (v) slow subsequent ‘sealing’ of the film pores by growth of boehmite crystals. Process (i) influences the available surface area, which increases proportionately (and very considerably) with the volume of liquid used for adsorption. The apparent activation energy of diffusion in the film falls with increase in size of the unsul‐phonated residue of a dye.

15Previous work identified gp56, encoded by the lytic bacteriophage SP01, as responsible for 16 inhibition of Bacillus subtilis cell division during its infection. Assembly of the essential tubulin-17 like protein FtsZ into a ring-shaped structure at the nascent site of cytokinesis determines the 18 timing and position of division in most bacteria. This FtsZ ring serves as a scaffold for 19 recruitment of other proteins into a mature division-competent structure permitting membrane 20 constriction and septal cell wall synthesis. Here we show that expression of the predicted 9.3-21 kDa gene product 56 (gp56) of SP01 inhibits latter stages of B. subtilis cell division without 22altering FtsZ ring assembly. GFP-tagged gp56 localizes to the membrane at the site of division. 48 complement. To achieve this, FtsZ assembly at mid-cell and subsequent division are highly 49 precise, with less than a 1% margin of error, suggesting a highly regulated process (2, 3). 50Blocking FtsZ assembly prevents membrane invagination and septal cell wall synthesis, leading 51 to filamentous, multinucleated cells and eventual cell death (4). 52 53As a conserved protein that is essential for division in most bacteria, FtsZ is an appealing target 54 of study for both physiologically relevant modes of its regulation and for potential development 55 of novel antibiotics (5-7). Included among cellular regulators of FtsZ assembly are proteins 56 encoded in regions of the E. coli genome that originally derived from phage, now turned 57 inactive. Cells have co-opted several of these so-called cryptic phage genes for increased host 58 fitness under particular conditions. These include dicB and dicF of cryptic phage Qin (aka phage 59 Kim) and the kilR (orfE) gene of cyptic phage Rac (8). The RNA product of dicF binds to ftsZ 60 mRNA to inhibit its translation (9), while the DicB peptide interacts with FtsZ inhibitor MinC 61 (10) to target ring assembly independently of its normal regulator MinD, but dependent on ZipA 62 (11). Transient division inhibition by cryptic DicB benefits the host by inhibiting phage receptor 63 proteins ManYZ, enhancing immunity to bacteriophage lambda infection by up to 100-fold (12). 64The KilR peptide of Rac inhibits E. coli division through an unknown Min-independent 65 mechanism that also causes increased loss of rod shape (13). 66 67 Functional bacteriophages also appear to encode factors that transiently block host cell division 68 during infection. Expression of the 0.4 gene of T7 phage or kil of lambda phage both lead to E. 69 coli cell filamentation through direct interference with FtsZ assembly by their protein products 70 (14-16). In both cases, temporary inhibition of host cytokinesis by the phage prior to host lysis 71 results in a subtle competitive advantage for the virus, although the specific nature of these 72 advantages remains unclear. 73 74 Although all of the above factors come from phage that infect E. coli, it is likely that cytokinesis 75 serves as a target for phage in the majority of other bacte...