Bacterial Quorum-Quenching Lactonase Hydrolyzes Fungal Mycotoxin and Reduces Pathogenicity of Penicillium expansum—Suggesting a Mechanism of Bacterial Antagonism

Abstract

Penicillium expansum is a necrotrophic wound fungal pathogen that secrets virulence factors to kill host cells including cell wall degrading enzymes (CWDEs), proteases, and mycotoxins such as patulin. During the interaction between P. expansum and its fruit host, these virulence factors are strictly modulated by intrinsic regulators and extrinsic environmental factors. In recent years, there has been a rapid increase in research on the molecular mechanisms of pathogenicity in P. expansum; however, less is known regarding the bacteria–fungal communication in the fruit environment that may affect pathogenicity. Many bacterial species use quorum-sensing (QS), a population density-dependent regulatory mechanism, to modulate the secretion of quorum-sensing signaling molecules (QSMs) as a method to control pathogenicity. N-acyl homoserine lactones (AHLs) are Gram-negative QSMs. Therefore, QS is considered an antivirulence target, and enzymes degrading these QSMs, named quorum-quenching enzymes, have potential antimicrobial properties. Here, we demonstrate that a bacterial AHL lactonase can also efficiently degrade a fungal mycotoxin. The mycotoxin is a lactone, patulin secreted by fungi such as P. expansum. The bacterial lactonase hydrolyzed patulin at high catalytic efficiency, with a kcat value of 0.724 ± 0.077 s-1 and KM value of 116 ± 33.98 μM. The calculated specific activity (kcat/KM) showed a value of 6.21 × 103 s−1M−1. While the incubation of P. expansum spores with the purified lactonase did not inhibit spore germination, it inhibited colonization by the pathogen in apples. Furthermore, adding the purified enzyme to P. expansum culture before infecting apples resulted in reduced expression of genes involved in patulin biosynthesis and fungal cell wall biosynthesis. Some AHL-secreting bacteria also express AHL lactonase. Here, phylogenetic and structural analysis was used to identify putative lactonase in P. expansum. Furthermore, following recombinant expression and purification of the newly identified fungal enzyme, its activity with patulin was verified. These results indicate a possible role for patulin and lactonases in inter-kingdom communication between fungi and bacteria involved in fungal colonization and antagonism and suggest that QQ lactonases can be used as potential antifungal post-harvest treatment.

Mining Lactonase Gene from Aflatoxin B1-Degrading Strain Bacillus megaterium and Degrading Properties of the Recombinant Enzyme

“…From this observation, we can speculate that AttM detoxifies AFB 1 mainly by disrupting the endolipid structure of AFB 1 . Dor et al demonstrated that bacterial AHL lactonases are also efficient in degrading mycotoxins . Pereyra, Martnez, and Cavaglieri showed that certain Bacillus species harbored the aii gene.…”

“…Dor et al demonstrated that bacterial AHL lactonases are also efficient in degrading mycotoxins. 46 Pereyra, Martnez, and Cavaglieri showed that certain Bacillus species harbored the aii gene. This gene encodes an acyl homoserine lactone (Ahl) lactonase, which can degrade AFB 1 .…”

Combination of Enzymes with Materials to Give Them Antimicrobial Features: Modern Trends and Perspectives

“…However, this enzyme has weak antimicrobial activity, so it is advisable to combine it with an antibiotic; for example, with polymyxin B. Loaded in this combination to bacterial cellulose, which has the potential to be used as a dressing material with a good absorbency, thermolysin noticeably improves the effect of the antibiotic action. Lactonases (EC 3.1.1) produced by various microorganisms have potential antibacterial properties mostly against Gram-negative pathogenic bacteria and catalyze the hydrolysis of AHL and fungal mycotoxins [ 68 , 69 , 70 , 71 , 72 ]. However, their use is most often limited by the thermal instability or low activity of these enzymes despite the presence of some thermostable variants; for example, natural lactonase (AidB) from Bosea sp.…”

Carrier Variety Used in Immobilization of His6-OPH Extends Its Application Areas

“…This interest is due to a possible increase in the level of food safety for humans and animals arising from their consumption of food and feeds contaminated with mycotoxins, respectively, due to their detoxification under mild conditions as a result of the action of various enzymatic catalysts [ 74 , 75 , 76 ]. It is already known today that lactonases may be among such potentially effective destructors [ 76 , 77 , 78 ], since individual mycotoxins contain lactone structures similar to AHLs in their structures. Since His 6 -OPH is active in relation to AHLs and catalyzes their hydrolysis similarly to well-known lactonases, this determines the interest in the enzyme under discussion as a possible destructor of not only AHLs but also mycotoxins with corresponding chemical structures.…”