Potential of AbiS as defence mechanism determined by conductivity measurement

Abstract

Aim: To compare pH and conductivity used in the determination of growth in reconstituted skim milk (RSM), to determine whether the presence of one or two plasmids in Lactococcus lactis had any influence on growth, and whether AbiS improved bacteriophages resistance of L. lactis. Methods and Results: Conductivity and pH were used to determine growth in RSM. A small increase in the generation time was found with increasing number of plasmids, while their size was unimportant. The introduction of a plasmid‐encoding AbiS did only enhance the level of phage resistance significant when other plasmids encoding either AbiS1 or the restriction modification system LlaBIII was present. Conclusions: The earliest detection of growth was observed by measuring pH, rather than conductance. The plasmid‐encoded AbiS system has a potential to be used as a phage resistance mechanisms in L. lactis during milk fermentations, especially when combined with other anti‐phage mechanisms. Significance and Impact of the Study: This study widened the knowledge about the influence of plasmid introduction on the growth rate of L. lactis, which is important for the construction of new strains. The level of protection against 936 groups of phages was only significant when the mechanism was present together with the RM system LlaBIII.

Characterisation of Lactococcus lactis isolates from herbs, fruits and vegetables for use as biopreservatives against Listeria monocytogenes in cheese

“…Therefore, their growth in milk is commonly determined by measurement of pH (Bachmann, Starrenburg, Molenaar, Kleerebezem, & Vlieg, 2012;Holubova & Josephsen, 2007). This method is based on the production of lactic acid which reduces the pH of milk when LAB grow.…”

“…This method is based on the production of lactic acid which reduces the pH of milk when LAB grow. Determination of LAB growth by pH measurement is faster and more economical than that of plate count method (Holubova & Josephsen, 2007). However, this view needs reconsideration because wild Lc.…”

Effect of the Abortive Infection Mechanism and Type III Toxin/Antitoxin System AbiQ on the Lytic Cycle of Lactococcus lactis Phages

“…Over 20 lactococcal abortive infection (Abi) systems have been reported (12)(13)(14)(15). While some Abi systems stop the replication of several phage genotypes, others inhibit only a few groups (12)(13)(14)(15). Of note, not every member of a phage group is sensitive to an Abi system at similar levels (14,16,17).…”

“…These hurdles can prevent the phage adsorption process, inhibit the phage genome ejection into the cell, cut the invading genome, or simply abort another step of the lytic cycle (11). Over 20 lactococcal abortive infection (Abi) systems have been reported (12)(13)(14)(15). While some Abi systems stop the replication of several phage genotypes, others inhibit only a few groups (12)(13)(14)(15).…”

Mutational Analysis of the Antitoxin in the Lactococcal Type III Toxin-Antitoxin System AbiQ

“…To date, an impressive number of distinct Abi systems have been identified in L. lactis (3)(4)(5)(6). These 23 systems are effective, at various degrees, against some or all prevalent groups of lactococcal phages (936, c2, and P335) found in dairy plants (3).…”