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Articles of Significant Interest Selected from This Issue by the Editors

Articles of Significant Interest Selected from This Issue by the Editors

Acclimatization of Methylocystis spp. to Salinity Change

Type II methanotrophs of the genus Methylocystis are widely distributed in upland soils, yet little is known about their ability to cope with fluctuations in soil salinity. Han et al. (e00866-17) showed that Methylocystis sp. strain SC2 is able to adapt to salt stress, but only within a narrow range of salinities. Exposed to 0.75% NaCl, its growth resumed within 24 h. The adaptive response involved differential expression of 301 genes and the accumulation of glutamate as an osmoprotectant. Presumably, these stress response mechanisms allow Methylocystis spp., such as strain SC2, to thrive in upland soils.

Wax Ester Biosynthesis in an Actinobacterium: a Potential Avenue to Sustainable, High-Value Lipids

Lipid-accumulating strains of bacteria have considerable potential for the sustainable production of high-value lipids such as wax esters, which are widely used in cosmetics and as lubricants. The lipid biosynthetic capabilities of rhodococci have long been recognized, but many aspects of this synthesis are poorly understood. Round et al. (e00902-17) identified a key enzyme in wax ester synthesis in rhodococci and exploited it to significantly improve the yield of these molecules. In doing so, this work contributes to the development of novel bioprocesses for an important class of oleochemicals.

Detection of Borrelia bavariensis in North American Seabird Colonies

Ticks transmit a wide range of pathogens, including Borrelia species spirochetes. Seabirds around the globe are commonly parasitized by the tick Ixodes uriae, which transmits Borrelia garinii among them. While investigating B. garinii transmission by I. uriae in seabird colonies of northeastern North America, Munro et al. (e01087-17) discovered that I. uriae ticks are also carrying Borrelia bavariensis. Previously, B. bavariensis was thought to be limited to tick and rodent host species in Eurasia. This expands the known geographic and host ranges for B. bavariensis and indicates that further investigations into this system are needed.

Unleashing Natural Competence in Lactococcus lactis

Specific bacterial species can internalize exogenous DNA, but this trait has not been observed for the dairy starter Lactococcus lactis. Mulder and colleagues (e01320-17) predicted the completeness of the competence gene sets in the genomes of specific L. lactis strains of both subspecies, and they showed that strains KF147, IL1403, and KW2 can internalize DNA upon overexpression of the competence regulator ComX. Similar data for strain KW2 were recently reported by David et al. (Appl Environ Microbiol 83:e01074-17, 2017, https://doi.org/10.1128/AEM.01074-17). Once the natural trigger is identified, natural competence can facilitate engineering strategies to harness the natural biodiversity in optimized starter strains.

New Lager Brewery Strains from Cachaça (Brazilian Spirit) Yeasts

The development of hybrids has been an effective approach to generate novel yeast strains with an optimal technological profile for use in beer production. Figueiredo et al. (e01582-17) described the generation of a new yeast strain for lager beer production by direct mating between two Saccharomyces cerevisiae strains isolated from cachaça distilleries: one strongly flocculent and other with a higher production of acetate esters. In this study, breeding/hybridization techniques were used to generate yeast strains that would be appropriate to produce new lager beers by exploring the capacity of cachaça yeast strains to flocculate and to ferment maltose at low temperatures with the concomitant production of flavoring compounds.

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