Bio-energetics Investigation of Candida albicans Using Real-time Extracellular Flux Analysis

Summary

Here, we present a stepwise protocol to investigate the mitochondrial respiration and glycolytic function in Candida Albicans using an extra flux analyzer.

Abstract

Mitochondria are essential organelles for the cellular metabolism and survival. A variety of key events take place in mitochondria, such as cellular respiration, oxidative metabolism, signal transduction, and apoptosis. Consequently, mitochondrial dysfunction is reported to play an important role in the antifungal drug tolerance and virulence of pathogenic fungi. Recent data have also led to the recognition of the importance of the mitochondria as an important contributor to fungal pathogenesis. Despite the importance of the mitochondria in fungal biology, standardized methods to understand its function are poorly developed. Here, we present a procedure to study the basal oxygen consumption rate (OCR), a measure of mitochondrial respiration, and extracellular acidification rates (ECAR), a measure of glycolytic function in C. albicans strains. The method described herein can be applied to any Candidaspp. strains without the need to purify mitochondria from the intact fungal cells. Furthermore, this protocol can also be customized to screen for inhibitors of mitochondrial function in C. albicans strains.

Introduction

Invasive fungal infections kill over 1.5 million people a year worldwide. This number is on the rise due to an increase in the numbers of people living with compromised immunity, including the elderly, premature infants, transplant recipients, and cancer patients¹. C. albicans is an opportunistic human fungal pathogen that is a part of the human microflora. It also inhabits mucosal surfaces and the gastrointestinal tract as a commensal organism. C. albicans produces serious systemic disease in people who have immune deficiencies, who have undergone surgery, or who have been treated with long courses of antibiotics. The Can....

Protocol

NOTE: The detailed stepwise protocol of the assay is described below, and the schematic protocol is shown in Figure 1.

1. C. albicans strains and growth conditions

1. Grow the C. albicans strains in liquid Yeast Extract-Peptone-Dextrose (YPD) medium at 30 °C in an incubator shaker overnight.
   NOTE: Maintain Candida strains as frozen stocks and grow on YPD agar (1 % yeast extract, 2% peptone, 2% dextrose, and 2% agar).

2. Preparation of reagents

1. Prepare the assay medium as follows:
   1. For mitochon....

Results

The focus of this protocol is to determine the bioenergetic functions of C. albicans assessed by extra flux analyzer. A C. albicans mutant lacking mitochondrial protein Mam33 is also included along with its complement strain, mam33Δ/Δ::MAM33 to study the effects of the deletion of a mitochondrial protein on OCR and ECAR. MAM33 encodes for a putative mitochondrial acidic matrix protein and its function in Candida is not known.

Discussion

The bioenergetics extra flux assay serves as an excellent tool to read out the mitochondrial function by measuring oxidative phosphorylation (OXPHOS)-dependent oxygen consumption in real-time. In addition, a glycolytic function which is measured as an extracellular acidification rate (change in extracellular pH) can also be investigated at the same time in real-time analysis.

Successful plating of C. albicans in the assay plate is one of the critical steps in the assay because the inc.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
RPMI 1640	Corning	MT50020PB
Antimycin A	Sigma	A8674
KCN
Mito stress kit	Agilent	103015-100
Oligomycin	Calbiochem	495455
pH meter	Accumet	AR20
Phenol red	Sigma	P5530
Poly-D lysine	Sigma	P6407
Rotenone	Santa cruz	203242
Seahorse XF24 FluxPak	Agilent	100850-001
SHAM
Sodium Chloride	Amresco	241
Sodium hydroxie pellets	J.T Baker	3722
Tissue culture grade water	Gibco	1523-0147
XF assay calibrant solution	Agilent	100840-000
Yeast extract Peptone Dextrose	Fisher scientific,	BP2469
Yeast extract Peptone Dextrose Agar	Sigma	A1296
Yeast extract Peptone Glycerol	Sigma	G2025