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Mycopathologia
Mycopathologia
Mycopathologia
0301-486X
1573-0832
Springer Netherlands Dordrecht

38622365
838
10.1007/s11046-024-00838-1
Mycopathologia GENOME
Draft Genome Sequence of Candida saopaulonensis from a Very Premature Infant with Sepsis
Ning Ya-Ting 12
Dai Rong-Chen 12
Luo Zheng-Yu 12
Xiao Meng 12
Xu Yingchun 12
Yan Qun yanqun@csu.edu.cn

3
Zhang Li zhanglipumchlab@163.com

12
1 grid.506261.6 0000 0001 0706 7839 Department of Laboratory Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730 China
2 grid.413106.1 0000 0000 9889 6335 Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, 100730 China
3 grid.452223.0 0000 0004 1757 7615 Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha, 410008 China
15 4 2024
15 4 2024
2024
189 3 3221 11 2023
23 2 2024
© The Author(s) 2024
https://creativecommons.org/licenses/by/4.0/ Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
The rare fungus Candida saopaulonensis has never been reported to be associated with human infection. We report the draft genome sequence of the first clinical isolate of C. saopaulonensis, which was isolated from a very premature infant with sepsis. This is the first genome assembly reaching the near-complete chromosomal level with structural annotation for this species, opening up avenues for exploring evolutionary patterns and genetic mechanisms of pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11046-024-00838-1.

Keywords

Candida saopaulonensis
Clinical case
Whole genome sequencing
Genome assembly
Annotation
Fungi
the National Key Research and Development Program of China2022YFC2303002 Zhang Li the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences2021-I2M-1-044 Zhang Li the National High Level Hospital Clinical Research Funding2022-PUMCH-C-052 Zhang Li issue-copyright-statement© Springer Nature B.V. 2024
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pmcThe rare fungus Candida saopaulonensis belongs to the Metschnikowiaceae clade, and is genetically most closely related to Candida picinguabensis. These two species are similar in morphology and physiology, but nucleotide differences, with 18 substitutions and three gaps in the D1/D2 domain of the large-subunit rDNA, warranted their classification as distinct species [1]. C. saopaulonensis was first isolated from water in the flower bracts in southeastern Brazil in 2000, and then found on corn plants in Thailand in 2016 [1, 2]. Human infections caused by this species have not been previously reported.

A 4-week-old male very premature infant, with gestational age of 29 weeks and birth weight of 780 g, was admitted for bronchopulmonary dysplasia. C. saopaulonensis was recovered from blood cultures obtained aseptically from the catheter hub on 3 June, 2019. The subculture demonstrated the phenotype of smooth globose colonies on Sabouraud dextrose medium (Thermoscientific, USA), and of ‘gray purple’ on Candida chromogenic medium (CHROMagar, France). Optical microscopy showed small round or ovoid cells, appearing singly or in the budding state. Formation of hyphae or pseudohyphae was not observed (Supplementary Fig. 1). Antifungal susceptibilities were tested using YeastOne Sensititre (Thermo Fisher, USA), and the minimum-inhibitory concentrations were as follows: fluconazole 0.12 mg/L, itraconazole 0.06 mg/L, voriconazole 0.008 mg/L, posaconazole ≤ 0.008 mg/L, micafungin 0.25 mg/L, anidulafungin 1 mg/L, caspofungin 0.5 mg/L, flucytosine ≤ 0.06 mg/L, and amphotericin B ≤ 0.12 mg/L.

This isolate (19XY460) was misidentified by Autof ms 1000 (Autobio Diagnostics Co., Ltd, China) as C. parapsilosis sensu stricto. Whole-genome sequencing of the isolate was carried out using Illumina MiSeq PE150 system, and data quality control and single nucleotide polymorphism (SNP) calling were performed as previously described [3]. Compared to the reference genome NRRL Y-27815 (GenBank assembly accession: GCA_030582915.1), a total of 100,171 SNP positions and 8455 insertion-deletion positions were identified in the genome of 19XY460. Alignment of the internal transcribed spacer (ITS) regions showed a 100% nucleotide identity of the sequence from isolate 19XY460 with that from C. saopaulonensis strain C6A (GenBank Accession No. KX781276.1), while it showed a 98.9% (370 bp /374 bp) identity with C. saopaulonensis type strain NRRL Y-27815; the latter comparison identified four differences, C281A, C282A, T283A, and C285T mutations, in the ITS regions of 19XY460 and NRRL Y-27815. There were no large-scale amplifications in this genome (Supplementary Fig. 2A). Ploidy analysis, visualized using the frequency of the non-reference allele across cumulative from heterozygous biallelic SNPs throughout all chromosomes [4], revealed that the isolate 19XY460 was haploid, characterized by almost entirely homozygous SNP sites (Supplementary Fig. 2B).

Long-read sequencing was performed using the PacBio Sequel II platform, and the data were assembled to the chromosomal level using Canu v2.2 [5]. The assembly was polished with next-generation sequencing data by Pilon v1.23 [6], and BUSCO v5.2.2 was used for quality control of assembly completeness [7]. The genome assembly resulted in eight scaffolds, with a total length of 12,068,158 bp (11.51 Mb), which was quite similar to the NRRL Y-27815 genome (12 Mb). The completeness of this genome reached 97.85%. GC content was 44.27%, and N50 was improved from 547,923 bp (NRRL Y-27815) to 2,019,073 bp (19XY460). The results of average nucleotide identity, determined with pyani tool, indicated that the genome of isolate 19XY460 had a 98.95% similarity with C. saopaulonensis strain NRRL Y-27815, and 95.64% similarity with the closely related fungus C. picinguabensis strain NRRL Y-27814 (Supplementary Fig. 2C&D). Structural annotation of the genome was conducted using AUGUSTUS v3.3.2 [8], then assessed using BUSCO v5.2.2 [7]. A total of 5006 genes were annotated on the chromosomes of 19XY460, achieving an annotation completeness of 96.17%. Additionally, the mitochondrial genome was assembled using GetOrganelle v1.7.7.0 [9], resulting in a circular sequence with a length of 41,901 bp and a GC content of 30.77%.

To the best of our knowledge, this is the first report of clinically relevant case caused by the rare fungal species C. saopaulonensis. We also describe the first genome assembly data of this species to the near-complete chromosomal level, complemented by structural annotation. As fungal diseases become more prevalent, this invaluable resource opens up avenues to delve into the evolutionary patterns and genetic mechanisms of pathogenesis of a potential new pathogen, C. saopaulonensis.

Supplementary Information

Below is the link to the electronic supplementary material.Supplementary file1 (DOCX 877 KB)

Author Contributions

YTN, MX and LZ conceived and planned the experiments. RCD performed genomic analysis. QY and ZYL collected the isolate and clinical data. YTN contributed to the first draft of the manuscript. YCX and LZ contributed to the review and editing.

Funding

This work was financially supported by the National Key Research and Development Program of China (2022YFC2303002), the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (2021-I2M-1-044), and the National High Level Hospital Clinical Research Funding (2022-PUMCH-C-052).

Data Availability

The isolate 19XY460 has been deposited at China Center of Industrial Culture Collection under the accession number CICC 33624 (http://www.china-cicc.org/cicc/detail2/?sid=14028). All sequencing data, assembly and annotation results have been deposited in the NCBI database (Biosample Number SAMN37476331, BioProject Number PRJNA1019270, Assembly Accession Number GCA_035610405.1, and ITS Accession Number PP123913.1). Data analysis and writing of article were in compliance with the MycopathologiaGENOMES quality assurance checklist [10].

Declarations

Ethics Approval

This study was approved by the Human Research Ethics Committee of Peking Union Medical College Hospital (Date: October 2022 / No. I-22PJ385).

Conflict of Interest

The authors have no relevant financial or non-financial interests to disclose.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Ya-Ting Ning and Rong-Chen Dai have contributed equally to this work.
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