Candida albicans Dispersed Cells Are Developmentally Distinct from Biofilm and Planktonic Cells

Abstract

Candida albicans surface-attached biofilms such as those formed on intravenous catheters with direct access to the bloodstream often serve as a nidus for continuous release of cells capable of initiating new infectious foci. We previously reported that cells dispersed from a biofilm are yeast cells that originate from the top-most hyphal layers of the biofilm. Compared to their planktonic counterparts, these biofilm dispersal yeast cells displayed enhanced virulence-associated characteristics and drug resistance. However, little is known about their molecular properties. To address that issue, in this study we aimed to define the molecular characteristics of these biofilm dispersal cells. We found that the inducer of dispersal, PES1, genetically interacts with the repressor of filamentation, NRG1, in a manner consistent with the definition of dispersed cells as yeast cells. Further, using a flow biofilm model, we performed comprehensive comparative RNA sequencing on freshly dispersed cells in order to identify unique transcriptomic characteristics. Gene expression analysis demonstrated that dispersed cells largely inherit a biofilm-like mRNA profile. Strikingly, however, dispersed cells seemed transcriptionally reprogrammed to acquire nutrients such as zinc and amino acids and to metabolize alternative carbon sources, while their biofilm-associated parent cells did not induce the same high-affinity transporters or express gluconeogenetic genes, despite exposure to the same nutritional signals. Collectively, the findings from this study characterize cell dispersal as an intrinsic step of biofilm development which generates propagules more adept at colonizing distant host sites. This developmental step anticipates the need for virulence-associated gene expression before the cells experience the associated external signals.

Screening the Drug:H+ Antiporter Family for a Role in Biofilm Formation in Candida glabrata

“…Interestingly, in C. albicans, MFS transporters, CaMdr1 and CaQdr1, have also been linked to biofilm formation and cell dispersion, being up-regulated in both conditions. It is suggested in the work of Uppuluri et al (2018) that the upregulation of these and other types of transporters is related to the reprogramming of dispersal cells to acquire nutrients and be able to attach and survive in nutrient-starved niches of the host (Uppuluri et al, 2018). It would be interesting to test if CgQdr2, CgTpo1_2, CgTpo4, and CgDtr1 have a role on this last phase of biofilm formation.…”

Extraction and purification of RNA from human carious dentine: an approach to enable bacterial gene expression studies

“…Considering the importance of a better understanding of the bacterial behavior in carious sites 2 , the current research established a methodology for RNA extraction and isolation to enable bacterial gene expression studies from human carious dentine samples. The majority of transcriptional studies of cariogenic bacteria was performed in planktonic cells in vitro and in vivo biofilms 7,9,11 , substrates where higher bacterial concentration is found when compared to dentine caries lesions 19 .…”

“…The majority of RNA-based investigations of oral microbiota analyzed only planktonic cells 4 , in vitro biofilms 5,6,7 or in vivo biofilms from rodent animals 8,9 . Although the first transcriptomic studies of human dental biofilm 10,11 and dentine 12,13 were carried out, just a few articles showed is given about technical procedures, RNA yield, purity and integrity from these human samples studies 13,14 . Besides, more attention has been requested about transcriptional studies in human dentinal caries, which can reflect the behavior of cariogenic bacteria in loco 2 .…”

Implications of the presence of yeasts in tracheobronchial secretions of critically ill intubated patients

“…The biofilm works as a reservoir for these microorganisms, representing an important etiological risk factor for pulmonary infections, due to the dispersion effect that occurs in parts of the biofilm, allowing translocation of these agents to the lower airways (Fernández-Barat et al, 2012[16]; Gil-Perotin et al, 2012[19]; Bassi et al, 2015[4]; Meligy et al, 2015[25]). Importantly, yeasts detached from the biofilm have an increased capacity of invasion (Uppuluri et al, 2018[40]) and thus pose a real risk of pulmonary infection.…”