In situ approaches show the limitation of the spoilage potential of Juniperus phoenicea L. essential oil against cold-tolerant Pseudomonas fluorescens KM24

Abstract

The present study aimed to elucidate the effect of subinhibitory concentrations (sub-MICs) of juniper essential oil (EO), α-pinene, and sabinene on the quorum-sensing (QS)–mediated proteolytic and lipolytic properties of Pseudomonas fluorescens KM24. These activities were verified under in situ conditions, in which sub-MICs of the agents altered the morphology of KM24 cells. RNA-Seq studies revealed key coding sequences (CDSs)/genes related to QS and the proteolytic/lipolytic activities of pseudomonads. In this work, all the examined agents decreased autoinducer synthesis and influenced the mRNA expression of the encoding acyltransferase genes lptA, lptD, and plsB. The highest reduction on the 3^rd and 5^th days of cultivation was observed for the genes lptD (−5.5 and −5.61, respectively) and lptA (−3.5 and −4.0, respectively) following treatment with EO. Inhibition of the lptA, lptD, and plsB genes by singular constituents of EO was on average, from −0.4 to −0.7. At 5 days of cultivation the profile of AHLs of the reference P. fluorescens KM24 strain consisted of 3-oxo-C14-HSL, 3-oxo-C6-HSL, C4-HSL, and N-[(RS)-3-hydroxybutyryl]-HSL, the concentrations of which were 0.570, 0.018, 3.744, and 0.554 μg ml⁻¹, respectively. Independent of the incubation time, EO, α-pinene, and sabinene also suppressed the protease genes prlC (−1.5, −0.5, and −0.5, respectively) and ctpB (−1.5, −0.7, and −0.4, respectively). Lipolysis and transcription of the lipA/lipB genes were downregulated by the agents on average from −0.3 to −0.6. α-Pinene- and sabinene-rich juniper EO acts as an anti-quorum-sensing agent and can repress the spoilage phenotype of pseudomonads.

Key points:

Juniper EO, α-pinene, sabinene exhibited anti-QS potential toward KM24.

RNA-Seq revealed key CDSs/genes related to QS/proteolytic/lipolytic activities of KM24.

Agents at sub-MIC levels influenced the mRNA expression of QS/lipase/protease genes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-021-11338-3.

STARCH GEL ELECTROPHORESIS OF MYOGEN FROM CHICKEN BREAST MUSCLE IN CONSTANT AND GRADIENT BUFFER SYSTEMS

By varying conditions of starch gel electrophoresis, factors contributing to the resolution of myogen proteins from chicken breast muscle have been studied. Variables examined included composition of the myogen extractant, protein concentration, ionic strength of electrophoretic media, pH of gel media, plane and direction of electrophoresis, and the nature of cations and anions in gel media and bridge solutions. The significance of anions was more closely studied with constant buffer systems, and gradient systems in which bridge electrolyte differed from, and gradually altered, the gel medium. Optimal separation was obtained in gradient systems with 0.10 M sodium chloride bridge solutions, and gel media of sodium cacodylate, pH 6.9, μ 0.010, which resolved 12 cationic zones, and sodium veronal, pH 7.4, μ 0.010, which resolved 10 anionic zones. These buffers in two-dimensional sequence revealed a total of about 24 components in this myogen.

STARCH GEL ELECTROPHORESIS OF MYOGEN FROM CHICKEN BREAST MUSCLE IN CONSTANT AND GRADIENT BUFFER SYSTEMS

By varying conditions of starch gel electrophoresis, factors contributing to the resolution of myogen proteins from chicken breast muscle have been studied. Variables examined included composition of the myogen extractant, protein concentration, ionic strength of electrophoretic media, pH of gel media, plane and direction of electrophoresis, and the nature of cations and anions in gel media and bridge solutions. The significance of anions was more closely studied with constant buffer systems, and gradient systems in which bridge electrolyte differed from, and gradually altered, the gel medium. Optimal separation was obtained in gradient systems with 0.10 M sodium chloride bridge solutions, and gel media of sodium cacodylate, pH 6.9, μ 0.010, which resolved 12 cationic zones, and sodium veronal, pH 7.4, μ 0.010, which resolved 10 anionic zones. These buffers in two-dimensional sequence revealed a total of about 24 components in this myogen.