Hyperpolarization and intracellular acidification in Trichoderma viride as a response to illumination

Isolation, characterization and mode of antimicrobial action againstVibrio choleraeof methyl gallate isolated fromAcacia farnesiana

“…Methyl gallate caused membrane hyperpolarization, which has been recognized as an important type of membrane damage (Yuroff et al 2003). The hyperpolarization could be explained as the result of an efflux of positively charged ions from the cytoplasm into the cell exterior, specifically K + , through a specific K + channel in the plasma membrane affecting cell homeostasis (Bot and Prodan 2009) or by the movement of negative charge from the extracellular space into the cytoplasm (Gresık et al 1991). This redistribution of K + would result in an increase in membrane potential, that is, a positive outside (Gresık et al 1991).…”

Trichoderma: sensing the environment for survival and dispersal

“…Conidiation induced by light and mechanical injury is strictly low pH-dependent, with maximum response values below pH 4.4 in T. atroviride, T. hamatum and T. pleuroticola (Steyaert et al, 2010b), whereas in T. harzianum, conidiation is higher at pH 5.5 (MorenoMateos et al, 2007); hence, the quality and quantity of the response seems to be species-specific. It is proposed that photoconidiation is dependent on a low intracellular pH, achieved by the low pH in the environment and the acidification that occurs when mycelia are exposed to light (Gresík et al, 1991;Steyaert et al, 2010b). Transcriptional regulation of gene expression by pH is mediated in filamentous fungi by the zinc finger transcription factor PacC (Peñalva & Arst, 2002.…”

Reproduction without sex: conidiation in the filamentous fungus Trichoderma

“…Low ambient pH of the growth medium has been demonstrated to result in intracellular acidification in Aspergillus niger and Saccharomyces cerevisiae (Caspani et al, 1985;Gradisnik-Grapulin & Legisa, 1997). In T. viride, intracellular acidification occurs when hyphae are exposed to light (Gresík et al, 1991); however, it is not known whether this response is constrained in a highly buffered environment. It is possible that on pH-buffered media the low ambient pH stimulates intracellular acidification and that light-induced acidification is constrained, whereas on the unbuffered medium light stimulates intracellular acidification, which brings the internal pH to below the threshold for photoconidiation.…”

“…These biochemical responses include changes in the membrane potential, intracellular acidification, a transient rise in ATP production, a biphasic rise in cAMP and an increase in the rate of oxygen consumption (Gresík et al, 1988(Gresík et al, , 1991Nemcovic & Farkas, 1998;Sulova et al, 1990). It has been suggested that these biochemical responses are part of the same physiological response; however, the exact order of events is uncertain.…”

“…It has been suggested that these biochemical responses are part of the same physiological response; however, the exact order of events is uncertain. Gresík et al (1991) put forward the following hypothesis regarding the biochemical changes associated with exposure to light. In T. viride, light triggers the opening of K + channels in the cellular membrane, which results in an efflux of K + ions into the outer membrane space, causing hyperpolarization.…”