Characteristics of O157:H7-specific infection bacteriophages (O157 coliphages) and broad-host-range bacteriophages for other serotypes (broad-host coliphages) were compared. The burst sizes of the two groups ranged from 40 to 176 PFU/infected cell. Distributions of the virulence factors ,, , and between the two groups were not differentiated. Broad-host-range coliphages showed lower stability at 70°C, in relation to O157 coliphages. However, O157 coliphages showed high acid and ethanol tolerance by reduction of only 22% and 11% phages, respectively, under pH 3 and 70% ethanol for 1 h exposure. Therefore, these results revealed that the O157 coliphages might be more stable under harsh environments, which might explain their effective infection of the acid-tolerant O157:H7.

We report herein a Lewis pair-catalyzed process for the regio- and stereoselective addition of secondary phosphine oxides (SPOs) to allenoates. A Lewis pair composed of B­(C6F5)3 and P­(4-OMeC6H4)3 dissociates into a free acid and base under reaction conditions, thereby creating key reaction intermediates that enable the atom-economical generation of an array of alkenylphosphorus building blocks. Mechanistic studies indicate that this process proceeds through a catalytic cycle wherein the deprotonation of a P–H bond of a SPO (coordinated to a boron catalyst) by the phosphonium zwitterion (resulting from the nucleophilic addition of a phosphine catalyst to allenoates) is the rate-determining step. Subsequent addition of the phosphinite anion to allenoate substrates furnishes β-addition products, while the reaction between the pair of the phosphinite anion and alkenylphosphonium cation affords γ-addition products.

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