Phenotypic evaluation of the effect of anaerobiosis on some virulence attributes of Candida albicans

Abstract

The current assumption that Candida albicans is a facultatively anaerobic organism has been widely accepted since its recovery from anoxic sites became common. However, the link between anaerobiosis and virulence remains uncertain. This study investigated the differential cell-surface hydrophobicity (CSH) using a hydrocarbon/water partition technique and analysed the differential secretion rates of secretory aspartyl proteases (Saps), esterase, chondroitinase and haemolysins of C. albicans strains recovered from periodontal pockets and non-periodontium-related intra-oral sites. For the enzymic tests, all strains from both sets were grown under aerobic and anaerobic conditions and the harvested cells were inoculated onto suitable normal or pre-reduced culture media in the presence or absence of molecular oxygen, respectively. The results showed that no variations were perceptible for CSH and chondroitinase (P .0.05). The secretion rates of esterase and haemolysins strongly decreased in an anoxic environment (P ,0.0001). However, a consistent increment (P ,0.0001) in Sap secretion was detected when cultures were grown under anaerobic conditions. Based on these results, it is suggested that the oxygen concentration in the atmosphere surrounding cells exerts a variable influence on the virulence attributes of C. albicans. INTRODUCTIONThe dimorphic fungus Candida albicans is the most commonly found eukaryotic micro-organism in the human oral cavity. The importance of this species in many oral mucosal diseases is well-known (McCullough et al., 1996) and most of the niches colonized by this fungus exhibit an oxygen tension and redox potential (E h ) compatible with those detected in environmental conditions favourable for the growth of aerobic or, in some instances, facultative organisms. One of the pioneering efforts to evaluate the possibility of anaerobic growth of C. albicans is attributed to Szawatkowski & Hamilton-Miller (1978), who reported that aerobically cultivable strains could also grow in the complete absence of atmospheric oxygen. Nowadays, even the mating behaviour of C. albicans during anaerobiosis is known (Dumitru et al., 2007).C. albicans has the ability to regulate individual complexes and partition electron flux among the classical respiratory chain, the parallel respiratory chain and an alternative oxidase, which allows its cells to modify their energy and redox status in order to ensure survival (Ruy et al., 2006). In the complete absence of oxygen, C. albicans cells may also use a fermentative pathway (Ogasawara et al., 2006), which implies a reduction in cell division rates.In recent years, interest in the lifestyle of Candida species in anoxic sites has increased. In the field of dentistry, many groups have shown that C. albicans is found in several oral niches that are not considered aerobic, such as periodontal pockets (Reynaud et al., 2001), radicular dentinal walls (Siqueira et al., 2002), infected root canals (Baumgartner et al., 2000), sites of apical periodontitis (Waltimo et al., 1997)...

Unsuspected pyocyanin effect in yeast under anaerobiosis

“…This species is capable of anaerobic growth in the presence of L‐cysteine (Rosa et al. ) and AF. Importantly, we found that high anaerobic PYO toxicity was also elicited in C. albicans (Fig.…”

“…The pathogenic crab-tree-negative yeast C. albicans was chosen because this fungus, together with Aspergillus fumigates, may coexist with P. aeruginosa in the lungs of cystic fibrosis (CF) patients (McAlester et al 2008). This species is capable of anaerobic growth in the presence of L-cysteine (Rosa et al 2008) and AF. Importantly, we found that high anaerobic PYO toxicity was also elicited in C. albicans (Fig.…”

Candida albicans survival and biofilm formation under starvation conditions

“…, Rosa et al . ) have previously been investigated individually; however, there is a gap in knowledge in terms of starvation survival of C. albicans under anaerobic conditions.…”

“…Its prevalence has been estimated to be 6% and 18% (Peciuliene et al 2001, Rôças et al 2008. This dimorphic fungus grows well in the presence of molecular oxygen but less well under low oxygen tension and negative redox potentials (Rosa et al 2008). Its adaptability to adverse environmental conditions and ability to form biofilms under such conditions are crucial for survival in the nutrient-deprived environment such as those prevailing in cleaned and filled root canals (Siqueira & Sen 2004).…”

Correlation of methylation of toll-like receptor 4 (TLR4) and interleukin-6 (IL6) promoter with insulin resistance in obese adolescents

“…34 Research on TLR4 promoter methylation at CpG -646 and -822 positions in the gingival tissues showed that almost the whole subjects in the regions were not methylated and were not associated with TLR-4 mRNA transcripts. 35 Because all subjects were not methylated in the region target of the TLR4 promoter, it can be concluded that there was no correlation between the degree of methylation in the TLR4 target region with insulin resistance in adolescents with obesity.…”