Phenotypic characteristics and transcriptome profile of Cryptococcus gattii biofilm

Eliandro Reis Tavares,Ulisses De Pádua Pereira,Gabriella Maria Andriani,Bárbara Gionco,Anderson Oliveira Do Carmo,Sueli Fumie Yamada-Ogatta,Lucy Megumi Yamauchi,Celso Vataru Nakamura,Ana Elisa Belotto Morguette,Phileno Pinge-Filho,Alexandre Tadachi Morey,Admilton Gonçalves De Oliveira,Galdino Andrade

doi:10.1038/s41598-019-42896-2

Abstract

In this study, we characterized Cryptococcus gattii biofilm formation in vitro. There was an increase in the density of metabolically active sessile cells up to 72 h of biofilm formation on polystyrene and glass surfaces. Scanning electron microscopy and confocal laser scanning microscopy analysis revealed that in the early stage of biofilm formation, yeast cells adhered to the abiotic surface as a monolayer. After 12 h, extracellular fibrils were observed projecting from C. gattii cells, connecting the yeast cells to each other and to the abiotic surface; mature biofilm consisted of a dense network of cells deeply encased in an extracellular polymeric matrix. These features were also observed in biofilms formed on polyvinyl chloride and silicone catheter surfaces. We used RNA-Seq-based transcriptome analysis to identify changes in gene expression associated with C. gattii biofilm at 48 h compared to the free-floating planktonic cells. Differential expression analysis showed that 97 and 224 transcripts were up-regulated and down-regulated in biofilm, respectively. Among the biological processes, the highest enriched term showed that the transcripts were associated with cellular metabolic processes, macromolecule biosynthetic processes and translation.

Highlights

Microbial biofilms are highly structured communities of surface-attached microorganisms encased in a self-produced extracellular polymeric matrix (EPM)
Like its sibling species C. neoformans, C. gattii is equipped with a wide arsenal of virulence determinants, and the main ones include the ability to grow at human body temperature; a polysaccharide capsule; expression of the enzymes laccase, superoxide dismutase, phospholipase and urease; and biofilm formation[5,33,34]
C. gattii infection shows the following characteristics: occurs more often in immunocompetent individuals; presents as an acute infection rather than reactivation disease; involves more often the lung, alone or concurrently with brain infection, where it frequently produces disease with focal biofilm-like structures known as cryptococcomas; produces large-mass lesions associated with central nervous system (CNS) complications, requiring prolonged therapy and/or surgical intervention[29,30,31,32]

Summary

Introduction

Microbial biofilms are highly structured communities of surface-attached microorganisms (sessile cells) encased in a self-produced extracellular polymeric matrix (EPM). Like its sibling species C. neoformans, C. gattii is equipped with a wide arsenal of virulence determinants, and the main ones include the ability to grow at human body temperature; a polysaccharide capsule (participates in the prevention of phagocytosis by human phagocyte cells and modulation of the immune response); expression of the enzymes laccase (responsible for the production of melanin), superoxide dismutase (provides protection against oxidative burst), phospholipase (participates in the destruction of surfactant molecules) and urease (participates in lung escape and dissemination to the central nervous system); and biofilm formation (infection by sessile cells of C. gattii causes a higher mortality rate of Galleria melonella larvae, a non-vertebrate model used for fungus-host interaction studies, when compared to infection caused by planktonic cells)[5,33,34]. The understanding of the mechanisms involved in the formation of C. gattii biofilm can contribute to the identification of new targets for developing strategies for its control

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