Respiratory pathways and oxygen toxicity in Phanerochaete chrysosporium

Zacchi, Laura

doi:10.1016/s0378-1097(99)00652-7

Cited by 1 publication

(3 citation statements)

References 15 publications

(20 reference statements)

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“…Collectively, our results are consistent with recent hypotheses in which oxidative stress conditions affect LIP synthesis in P. chrysosporium (35,36,(44)(45)(46). Rothschild et al (36) suggested that Mn deficiency increases the level of oxygen radicals generated within the cell.…”

Section: Discussionsupporting

confidence: 93%

“…Rothschild et al (36) suggested that Mn deficiency increases the level of oxygen radicals generated within the cell. Zacchi et al (44)(45)(46) reported a major loss in organization of cellular structure, possibly due to oxygen toxicity, in carbon-limited cultures of P. chrysosporium exposed to an atmosphere of pure O 2, which implies that LIP may be synthesized in response to oxidative stress.…”

Section: Discussionmentioning

confidence: 99%

“…The high O 2 concentration presumably leads to increased production of reactive oxygen species (ROS) relative to that during normal metabolism, subjecting the fungus to a ROS-rich environment, in addition to the toxic radical intermediates produced in the ligninolytic phase. Zacchi et al (44)(45)(46) suggested that cultures of P. chrysosporium exposed to O 2 to trigger LIP synthesis are subjected to oxygen toxicity, which leads to disorganization of the cellular ultrastructure and chlamydospore development, probably in response to accumulating ROS. LIP activities were similar in cultures of P. chrysosporium exposed to pure O 2 gas (oxygenated cultures) and in manganese-deficient cultures grown with atmospheric air (36).…”

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Reactive Oxygen Species and Induction of Lignin Peroxidase in Phanerochaete chrysosporium

Belinky

Flikshtein

Lechenko

et al. 2003

Appl Environ Microbiol

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We studied oxidative stress in lignin peroxidase (LIP)-producing cultures (cultures flushed with pure O 2 ) of Phanerochaete chrysosporium by comparing levels of reactive oxygen species (ROS), cumulative oxidative damage, and antioxidant enzymes with those found in non-LIP-producing cultures (cultures grown with free exchange of atmospheric air [control cultures]). A significant increase in the intracellular peroxide concentration and the degree of oxidative damage to macromolecules, e.g., DNA, lipids, and proteins, was observed when the fungus was exposed to pure O 2 gas. The specific activities of manganese superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase and the consumption of glutathione were all higher in cultures exposed to pure O 2 (oxygenated cultures) than in cultures grown with atmospheric air. Significantly higher gene expression of the LIP-H2 isozyme occurred in the oxygenated cultures. A hydroxyl radical scavenger, dimethyl sulfoxide (50 mM), added to the culture every 12 h, completely abolished LIP expression at the mRNA and protein levels. This effect was confirmed by in situ generation of hydroxyl radicals via the Fenton reaction, which significantly enhanced LIP expression. The level of intracellular cyclic AMP (cAMP) was correlated with the starvation conditions regardless of the oxygenation regimen applied, and similar cAMP levels were obtained at high O 2 concentrations and in cultures grown with atmospheric air. These results suggest that even though cAMP is a prerequisite for LIP expression, high levels of ROS, preferentially hydroxyl radicals, are required to trigger LIP synthesis. Thus, the induction of LIP expression by O 2 is at least partially mediated by the intracellular ROS.The white rot fungus Phanerochaete chrysosporium can degrade and metabolize lignin and a broad range of recalcitrant organopollutants (14, 34). Lignin depolymerization is achieved primarily by one-electron oxidation reactions catalyzed by extracellular oxidases and peroxidases in the presence of extracellular hydrogen peroxide (H 2 O 2 ). Lignin peroxidase (LIP) is an enzyme commonly associated with the extracellular degradation of lignin by P. chrysosporium. It oxidizes phenols to phenoxy radicals and nonphenolic aromatics to radical cations (6,21). Liquid cultures of P. chrysosporium must be starved (nitrogen or carbon depletion) and exposed to a pure O 2 atmosphere to trigger LIP expression (4, 11, 26). Boominathan and Reddy (7) showed that transcription of genes encoding some LIP enzymes is controlled by cyclic AMP (cAMP) levels.Increasing oxygen availability to liquid cultures of P. chrysosporium increases LIP levels (35, 36). The high O 2 concentration presumably leads to increased production of reactive oxygen species (ROS) relative to that during normal metabolism, subjecting the fungus to a ROS-rich environment, in addition to the toxic radical intermediates produced in the ligninolytic phase. suggested that cultures of P. chrysosporium exposed to O 2 to trigger LIP synt...

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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