Candida blankii

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1. Classification

a. Higher order taxa

Domain Eukarya
Kingdom Fungi
Phylum Ascomycota
Class Saccharomycetes
Order Saccharomycetales
Family Saccharomycetaceae
Genus Candida
Species blankii


2. Description and significance

Candida blankii is an opportunistic fungal pathogen that has infected at least three patients worldwide as of 2018 [2] [3]. The patients who have been infected with C. blankii are adolescents with cystic fibrosis and one preterm neonate with respiratory difficulties [2] [3]. Once infected with C. blankii, patients develop C. blankii fungaemia, a blood condition characterized by the presence of fungal populations in the circulatory system [2]. This condition can be problematic, since immunosuppressed and immunocompromised patients are most susceptible and the C. blankii population is resistant to azole antibacterial medications [2]. Doctors in Brazil have identified polyene antifungals as a potential treatment for C. blankii fungaemia [3]. Although C. blankii is a newly identified pathogenic threat to persons with respiratory issues, it is thought that there may have been some missed cases due to insufficient diagnosis techniques in previous years [2].

3. Cell and Genome structure

C. blankii isolates form typical yeast-like cream-colored colonies that develop a pink color on Sabouraud dextrose agar, and then later turn dark blue [2]. The dark blue color is similar to the species Candida tropicalis and the pink color is similar to both Candida auris and Candida haemulonii [2]. C. blankii can be identified in patients by sequencing of the 26S ribosomal subunit DNA from blood samples [2]. The D1D2 rRNA sequence is conserved across strains of C. blankii [2]. Further information on the genome structure, coding regions, gene expression, and cell structure of Candida blankii are not well understood and/or not accessible to the academic community at this time.

4. Ecology

C. blankii has been found mainly associated with the human respiratory system, where it acts as an obligate pathogen [2] [3] Before associating with humans, C. blankii originated in the organs of mink [3] . In these organisms, C. blankii had devastating effects and in all cases observed, caused death. C. blankii also forms symbiotic relationships with other organisms; the main example explored was discovered in India between pollinating bees, Azadirachta indica, and C. blankii [4]. In this symbiotic relationship, C. blankii is found on the nectary glands of the flower, A. indica, that bees pollinate. This relationship is not fully understood yet; however, it has been shown that A. indica flowers more in the presence of C. blankii [4]

5. Metabolic processes

C. blankii is aerobic and is known to oxidize many alcohols, carbohydrates, amino acids, and other organic compounds [5]. Use of C. blankii as a biosensor for BOD (biochemical oxygen demand) to determine water quality was explored and compared to two other Candida species [5]. Biosensing is dependent on the metabolism of the organism [5]. C. blankii has a longer lag phase (hour 0-14) and exponential growth phase (hour 14-38) compared to the two other Candida species [5]. The overall maximum oxidative activity throughout the lifespan of the C. blankii is about 18 hours in total [5]. The optimal pH for C. blankii to elicit a biosensor response is at 6.8, which indicates a slightly acidic preference [5]. C. blankii is inhibited by two heavy metal ions, Ni2+ and Cr(IV), which decrease its oxidative activity [5]. C. blankii’s biosensor activity declines by 50% in just eight days, which suggests only short-term stability of its receptor elements and therefore limits practical applications of the organism for such purpose [5].

6. Pathology

C. blankii was identified in several recent papers on pulmonary infection cases, including cystic fibrosis and lung transplant patients [2]. C. blankii is an opportunistic pathogen present in the blood and is not native to the human body’s mucous membranes [2]. The presence of C. blankii in the blood was confirmed by DNA sequencing of blood culture isolates from patients after development of sepsis and fungaemia [2]. C. blankii is a particularly troublesome fungus in that it is resistant to azole-containing antifungal drugs, including fluconazole and voriconazole as well as β-glucan synthase inhibitors anidulafungin and micafungin [2] [3]. The fungus however does show some sensitivity to amphotericin, however this is not relevant clinically [2]. Although C. blankii shows reduced susceptibility to echinocandin antibacterials relative to other Candida, positive treatment outcomes can be achieved with these regiments [3].

7. Current Research

There have been few studies done on C. blankii that have implications for therapeutic development. Candida blankii is considered an opportunistic pathogen and has been found to be resistant to common antifungal compounds [3]. For example, a study done on a 16 year-old patient with cystic fibrosis [3]. Following a lung transplant, the patient had a bloodstream infection caused by Candida blankii [3]. The species was identified following sequence analysis of its 26S subunit rRNA.3 Then antifungal susceptibility testing was performed on the species using various inhibitory drugs, which showed limited activity against C. blankii [3]. Also, the organism showed high inhibitory concentrations of different types of azoles, allowing the authors to advise against using azoles for treatments of C. blankii in patients [3]. This demonstrates that C. blankii is an opportunistic pathogen for patients that undergo lung transplants and that are diagnosed with cystic fibrosis.

There is a potential inhibitor of Candida blankii that can be used for various medical applications [6]. Candida blankii was cultivated in mixed medium of wood hydrolysate and whey [6]. Within this medium, an inhibitor, furfural was found [6]. This research team had found that treatment of furfural to a strain of Candida blankii affected cell functions and the biomass and the protein yield dramatically decreased [6]. The inhibitor effect was dependent on both concentration and the dilution rate [6]. This finding has implications for therapeutic development that could aid patients infected with this organism.

Further research has been done investigating C. blankii’s uses in industry, particularly in fumaric acid production [7]. As early as 1978, C. blankii was shown to produce fumaric acid by fermentation [7]. In 1999, C. blankii was utilized to produce fumaric acid from hydrocarbon paraffins provided from kerosene supplementation [7]. Optimal conditions for high yield fumaric acid production include glucose (60 g/L), ammonium chloride at 0.2 g/L, 30°C, leading to an overall yield of 60% [7]. High supplements of nitrogen stopped fumaric acid production and significantly decreased overall yield [7]. It was concluded that optimal conditions involved high concentrations of carbon sources and low concentrations of nitrogen sources, as the process is dependent on the population of the yeast being stagnant and hence growth limited [7]. Further research is needed to determine the applications of C. blankii in fumaric acid production using bioreactors, however the sensitivity of the process may be a limiting factor.

This student page has not been curated.

Edited by Andrew Cyr, Stephanie Esonwune, Kathryn Satko, and Kara Sevola, students of Jennifer Talbot for BI311 General Microbiology, 2018, Boston University

8. References

  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 Al-Haqqan, A., Al-Sweih, N., Ahmad, S., Khan, S., Joseph, L., Varghese, S., & Khan, Z. 2018. Azole-resistant Candida blankii as a newly recognized cause of bloodstream infection. New Microbes and New Infections, 26: 25-29.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Nobrega de Almeida, J., Campos, S. V., Thomaz, D. Y., Thomaz, L., de Almeida, R. K. G., Del Negro, G. M. B., … Benard, G. (2018). Candida blankii: an emergent opportunistic yeast with reduced susceptibility to antifungals. Emerging Microbes & Infections, 7, 24.
  4. 4.0 4.1 Sandhu, D. K & Waraich, M. K. (1985). Yeasts Associated with Pollinating Bees and Flower Nectar. Microbial Ecology. 11:51-58.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Arlyapov, B. Kamanin, S. Ponamoreva, O. Reshetilov, A. 2012. Biosensor analyzer for BOD index express control on the basis of the yeast microorganisms Candida maltosa, Candida blankii, and Debaryomyces hansenii. Enzyme and Microbial Technology, 50, 215-220.
  6. 6.0 6.1 6.2 6.3 6.4 Tzvetkova, B., Hristozova, T., Angelov, A., and Paskaleva, D. 2004. Effect of furfural on the growth of lactose-utilizing Candida Blankii 35. World Journal of Microbiology and Biotechnology, 20(3): 219-223.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 K. Tsekova, A. Kaimaktchiev & A. Krumov (1999) Production of Fumaric Acid from n-Alcanes by Candida Blankii NA-83, Biotechnology & Biotechnological Equipment, 13:2, 24-26.