Transcriptome Reveals Regulation of Quorum Sensing of Hafnia alvei H4 on the Coculture System of Hafnia alvei H4 and Pseudomonas fluorescens ATCC13525

Abstract

In the food industry, foodborne spoilage bacteria often live in mixed species and attach to each other, leading to changes in spoilage characteristics. Quorum sensing (QS) has been reported to be a regulating mechanism for food spoiling by certain kinds of bacteria. Here, the contents of biofilm, extracellular polysaccharides, and biogenic amines in the coculture system of Hafnia alvei H4 and Pseudomonas fluorescens ATCC13525 were significantly reduced when the QS element of H. alvei H4 was deleted, confirming that QS of H. alvei H4 is involved in the dual-species interactions. Then, transcriptomics was used to explore the regulatory mechanism at the mRNA molecular level. The deletion of the QS element decreased the transcript levels of genes related to chemotaxis, flagellar assembly, and the two-component system pathway of H. alvei H4 in the coculture system. Furthermore, a total of 732 DEGs of P. fluorescens ATCC13525 were regulated in the dual species, which were primarily concerned with biofilm formation, ATP-binding cassette transporters, and amino acid metabolism. Taken together, the absence of the QS element of H. alvei H4 weakened the mutual cooperation of the two bacteria in the coculture system, making it a good target for managing infection with H. alvei and P. fluorescens.

The Phase-Dependent Regulation of Lux-Type Genes on the Spoilage Characteristics of Hafnia alvei

“…As shown in Figure 6 A, after 72 h of culture, the maximum concentration of cadaverine produced by wild strains was 252.7 mg/L, while the cadaverine concentrations of Δ luxI , Δ luxR and Δ luxIR were 194.5 mg/L, 175.1 mg/L and 154.2 mg/L, respectively, indicating that the luxI and luxR genes have a potential upregulation on the production of cadaverine. According to Wang’s work [ 26 ], similar results were obtained, where the amounts of putrescine and cadaverine of Δ luxI strains were always lower ( p < 0.05) compared with wild-type H. alvei H4. The cadaverine concentrations of different phenotypic strains at 0–96 h were used as the basis neuron for SOM analysis in Figure 6 B.…”

“…As shown in Figure 6A, after 72 h of culture, the maximum concentration of cadaverine produced by wild strains was 252.7 mg/L, while the cadaverine concentrations of ΔluxI, ΔluxR and ΔluxIR were 194.5 mg/L, 175.1 mg/L and 154.2 mg/L, respectively, indicating that the luxI and luxR genes have a potential upregulation on the production of cadaverine. According to Wang's work [26], similar results were obtained, where the amounts of putrescine and cadaverine of ΔluxI strains were always lower (p < Likewise, the influence of the luxI and luxR genes on cadaverine production was specifically analyzed. As shown in Figure 6A, after 72 h of culture, the maximum concentration of cadaverine produced by wild strains was 252.7 mg/L, while the cadaverine concentrations of ∆luxI, ∆luxR and ∆luxIR were 194.5 mg/L, 175.1 mg/L and 154.2 mg/L, respectively, indicating that the luxI and luxR genes have a potential upregulation on the production of cadaverine.…”

“…The determination of BAs was conducted based on the work of Wang et al [ 26 ]. H. alvei H4 strains (wild type, Δ luxI , Δ luxR and Δ luxIR ) were cultivated in LB supplemented with 0.005% pyridoxal-5-phosphate and 0.1% precursor amino acid for 24 h. Then 1 mL of culture was mixed with 9 mL 10% trichloroacetic acid in a centrifuge tube.…”