Differences between Cryptococcus neoformans and Cryptococcus gattii in the Molecular Mechanisms Governing Utilization of D-Amino Acids as the Sole Nitrogen Source

AbstractHomoserine dehydrogenase (HSD) is a key enzyme in the synthesis pathway of the aspartate family of amino acids. HSD can catalyze the reversible reaction of L-aspartate-β-semialdehyde (L-ASA) to L-homoserine (L-Hse). In direct contrast, growth characteristic studies of some bacterial such as Arthrobacter nicotinovorans showed that the bacterium could grow well in medium with L-homoserine as sole carbon, nitrogen and energy source, but the genes responsible for the degradation of L-Hse remain unknown. Based on the function and sequence analysis of HSD, one putative homoserine dehydrogenase from A.nicotinovorans was named AnHSD, which was different from those HSDs that from the aspartic acid metabolic pathway, might be responsible for the degradation of L-Hse. Surprisingly, the analysis showed that the purified AnHSD exhibited specific L-Hse oxidation activity without reducing activity. At pH 10.0 and 40 °C, The Km and Kcat of AnHSD was 6.30 ± 1.03 mM and 462.71 s-1, respectively. AnHSD was partiality for NAD+ cofactor, as well as insensitive to feedback inhibition of downstream amino acids of aspartic acid family. The physiological role of AnHSD in A.nicotinovorans is discussed. These findings provide a novel insight for a better understanding of an alternative genetic pathway for L-Hse catabolism which was dominated by the novel HSD.ImportanceL-homoserine is an important building block for the synthesis of L-threonine, L-methionine, L-lysine which from aspartic acid family amino acids. However, some bacteria can make use of L-homoserine as a sole carbon and nitrogen source. Although the microbial degradation of L-homoserine has been studied several times, the genes involved and the molecular mechanisms remain unclear. In this study, we show that AnHSD responsible for the catabolism of L-homoserine in strain Arthrobacter nicotinovorans, as a special homoserine dehydrogenase with high diversity exists in Arthrobacter, Microbacterium, Rhizobium. We report for the first time that this novel homoserine dehydrogenase is now proposed to play a crucial role in that L-homoserine can use as a sole carbon and nitrogen source. This study is aimed at elucidating the enzymatic properties and function features of homoserine dehydrogenase from Arthrobacter nicotinovorans. These findings provide new insight into the catabolism of L-homoserine in bacteria.

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The capability of the algaeChlorella vulgaris andScenedesmus obliquus of utilizing amino acids as the sole nitrogen source

Biologia Plantarum ◽

10.1007/bf02878236 ◽

1979 ◽

Vol 21 (5) ◽

pp. 372-375 ◽

Cited By ~ 1

Author(s):

Jiřina Dvořáková

Keyword(s):

Amino Acids ◽

Nitrogen Source ◽

Sole Nitrogen Source

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Identification of a novel gene, URE2, that functionally complements a urease-negative clinical strain of Cryptococcus neoformans

Microbiology ◽

10.1099/mic.0.2006/000133-0 ◽

2006 ◽

Vol 152 (12) ◽

pp. 3723-3731 ◽

Cited By ~ 11

Author(s):

Ashok Varma ◽

Shaoxi Wu ◽

Ningru Guo ◽

Wanqing Liao ◽

Guxia Lu ◽

...

Keyword(s):

Nitrogen Source ◽

Cryptococcus Neoformans ◽

Genomic Library ◽

Central Nervous System Infection ◽

Immunocompetent Patient ◽

Clinical Strain ◽

Sole Nitrogen Source ◽

Wild Type ◽

Genomic Databases ◽

Serotype A

A urease-negative serotype A strain of Cryptococcus neoformans (B-4587) was isolated from the cerebrospinal fluid of an immunocompetent patient with a central nervous system infection. The URE1 gene encoding urease failed to complement the mutant phenotype. Urease-positive clones of B-4587 obtained by complementing with a genomic library of strain H99 harboured an episomal plasmid containing DNA inserts with homology to the sudA gene of Aspergillus nidulans. The gene harboured by these plasmids was named URE2 since it enabled the transformants to grow on media containing urea as the sole nitrogen source while the transformants with an empty vector failed to grow. Transformation of strain B-4587 with a plasmid construct containing a truncated version of the URE2 gene failed to complement the urease-negative phenotype. Disruption of the native URE2 gene in a wild-type serotype A strain H99 and a serotype D strain LP1 of C. neoformans resulted in the inability of the strains to grow on media containing urea as the sole nitrogen source, suggesting that the URE2 gene product is involved in the utilization of urea by the organism. Virulence in mice of the urease-negative isolate B-4587, the urease-positive transformants containing the wild-type copy of the URE2 gene, and the urease-negative vector-only transformants was comparable to that of the H99 strain of C. neoformans regardless of the infection route. Virulence of the URE2 disruption stain of H99 was slightly reduced compared to the wild-type strain in the intravenous model but was significantly attenuated in the inhalation model. These results indicate that the importance of urease activity in pathogenicity varies depending on the strains of C. neoformans used and/or the route of infection. Furthermore, this study shows that complementation cloning can serve as a useful tool to functionally identify genes such as URE2 that have otherwise been annotated as hypothetical proteins in genomic databases.

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Effect of D-amino acids on conidium size and numbers of pseudosepta per conidium in isolates of Bipolaris sorokiniana

Canadian Journal of Botany ◽

10.1139/b75-075 ◽

1975 ◽

Vol 53 (7) ◽

pp. 600-603 ◽

Cited By ~ 9

Author(s):

Howard Harding

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Nitrogen Source ◽

Aspartic Acid ◽

Large Range ◽

Correlation Coefficients ◽

Bipolaris Sorokiniana ◽

Sole Nitrogen Source ◽

Consistent Relationship

Isolates of Bipolaris sorokiniana grew to some extent on the D-isomers of 15 amino acids supplied as the sole nitrogen source. D-histidine did not support growth of any isolate. No conidia were produced by cultures grown on D-arginine. There was no consistent relationship between length of conidia produced by D- and L-isomers of the same amino acid. The trend was towards the production of shorter conidia on D-amino acids, although isolates varied considerably in their response. Conidia produced on D-phenylalanine were markedly shorter than those produced on the L-isomer, although isolates varied in the magnitude of response. A similar effect was recorded with aspartic acid as the nitrogen source but only in buffered medium. Conidia produced on D-ornithine were longer than those produced on L-ornithine, although this response was less-marked in buffered medium. Generally, the numbers of pseudosepta per conidium were higher in conidia produced on the L-isomer of individual amino acids. Although this increase in numbers usually paralleled the increased length of conidia, there was a large range in correlation coefficients between the two values over different isolate–substrate combinations.

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Phytochemical Constituents of Tulbaghia violacea Harv Extract and its Antifungal Potential Against Cryptococcus neoformans and Cryptococcus gattii

The Natural Products Journal ◽

10.2174/2210315509666181214154345 ◽

2019 ◽

Vol 9 (4) ◽

pp. 330-340

Author(s):

Mitradev Pattoo ◽

Vuyokazi Belewa ◽

Benesh Munilal Somai

Keyword(s):

Antifungal Activity ◽

Cryptococcus Neoformans ◽

Antifungal Therapy ◽

Developing World ◽

Chemical Constituents ◽

Cryptococcus Gattii ◽

Plant Part ◽

Aqueous Extracts ◽

Antifungal Activities ◽

Antifungal Potential

Background:In both the developed and developing world, the mortality rates of people afflicted with cryptococcosis are unacceptably high despite the availability of antifungal therapy. The disease is caused by Cryptococcus neoformans (predominantly in immunocompromised individuals) and by Cryptococcus gattii. Globally the disease is estimated to cause around 600,000 deaths annually. Antifungal therapy is available, but in the developing world, may be unaffordable to many people, there is an increasing threat of resistance to the available drugs and our repertoire of antifungal drugs is very limited. Consequently, more research has been focusing on the use of medicinal plants as therapeutic agents. The originality of the current study is that although Tulbaghia violacea is a well-documented medicinal plant, the chemical composition of aqueous extracts and their antifungal potential against pathogenic yeasts are unknown. This is the first study that evaluates the chemical constituents of aqueous T. violacea root, leaf, rhizome and tuber extracts and their corresponding antifungal activities against C. neoformans and C. gattii.Objectives:The study aimed to investigate the phytochemical composition and antifungal potential of Tulbaghia violacea root, leaf, rhizome and tuber extracts against Cryptococcus neoformans and Cryptococcus gattii.Methods:Roots, leaves, rhizomes and tubers were extracted with water only for 48 h at room temperature with continuous shaking. Extracts were filter sterilized, freeze-dried and, chemically analyzed for saponin, flavonol, phenolic and tannin content. Chemical constituents of each extract were also identified by GC-MS analysis. The Minimum Inhibitory Concentration (MIC) of suitably diluted extracts of each plant part were also performed against C. neoformans and C. gattii, yeast pathogens commonly associated with HIV/AIDS sufferers.Results:Phytochemical analysis showed different concentrations of saponins (between 1023 and 2896.73 µg/ml), phenolics (between 16.48 and 51.58 µg/ml) and tannins (between 122.30 and 543.07 µg/ml) present in the different extracts. No flavonols were detected. GC-MS analysis identified a complex mixture of phytochemicals composed predominantly of sulphide, pyran, furan and ketone containing compounds to be present in the different plant parts. All extracts were dominated by the presence of 4 H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl, a pyran known to have antifungal properties. Although the root, leaf, rhizome and tuber extracts exhibited antifungal activities against both fungi, the rhizome and tuber extract were found to possess the lowest MIC’s of 1.25 mg/ml and 2.5 mg/ml against Cryptococcus neoformans and Cryptococcus gattii respectively.Conclusion:T. violacea extracts have a complex constituent of phytochemicals and each plant part exhibited a strong antifungal activity against C. neoformans and C. gattii. The rhizome and tuber extracts showed the highest antifungal activity against C. neoformans and C. gattii respectively. Thus, T. violacea aqueous extracts are strong candidates for further development into an antifungal chemotherapeutic agent.

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Access to 2-Arylquinazolines via Catabolism/Reconstruction of Amino Acids with Insertion of Dimethyl Sulfoxide

Chemical Communications ◽

10.1039/d1cc00623a ◽

2021 ◽

Author(s):

Jin-Tian Ma ◽

Li-Sheng Wang ◽

Zhi Chai ◽

Xin-Feng Chen ◽

Bo-Cheng Tang ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Dimethyl Sulfoxide ◽

Nitrogen Source ◽

Carbon And Nitrogen ◽

First Time

Quinazoline skeletons are synthesized by amino acids catabolism/reconstruction combined with dimethyl sulfoxide insertion/cyclization for the first time. The amino acid acts as a carbon and nitrogen source through HI-mediated catabolism...

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Environmental Status of Cryptococcus neoformans and Cryptococcus gattii in Colombia

Journal of Fungi ◽

10.3390/jof7060410 ◽

2021 ◽

Vol 7 (6) ◽

pp. 410

Author(s):

Briggith-Nathalia Serna-Espinosa ◽

Diomedes Guzmán-Sanabria ◽

Maribel Forero-Castro ◽

Patricia Escandón ◽

Zilpa Adriana Sánchez-Quitian

Keyword(s):

Cryptococcus Neoformans ◽

Species Complex ◽

Columba Livia ◽

Systematic Investigation ◽

Cryptococcus Gattii ◽

Eucalyptus Species ◽

Environmental Niche ◽

Worldwide Distribution ◽

Bird Droppings ◽

The Central Nervous System

The genus Cryptococcus comprises more than 80 species, including C. neoformans and C. gattii, which are pathogenic to humans, mainly affecting the central nervous system. The two species differ in geographic distribution and environmental niche. C. neoformans has a worldwide distribution and is often isolated from bird droppings. On the contrary, C. gattii is reported in tropical and subtropical regions and is associated with Eucalyptus species. This review aims to describe the distribution of environmental isolates of the Cryptococcus neoformans species complex and the Cryptococcus gattii species complex in Colombia. A systematic investigation was carried out using different databases, excluding studies of clinical isolates reported in the country. The complex of the species of C. gattii is recovered mainly from trees of the genus Eucalyptus spp., while the complex of the species of C. neoformans is recovered mainly from avian excrement, primarily Columba livia (pigeons) excrement. In addition, greater positivity was found at high levels of relative humidity. Likewise, an association was observed between the presence of the fungus in places with little insolation and cold or temperate temperatures compared to regions with high temperatures.

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PRODUCTION OF CYTASES ACTIVE ON BARLEY GUM BY BACTERIA OF THE GENUS BACILLUS

Canadian Journal of Botany ◽

10.1139/b53-004 ◽

1953 ◽

Vol 31 (1) ◽

pp. 28-32 ◽

Cited By ~ 1

Author(s):

A. C. Blackwood

Keyword(s):

Bacillus Subtilis ◽

Enzymatic Activity ◽

Nitrogen Source ◽

Freeze Drying ◽

Shake Flask ◽

Sole Nitrogen Source ◽

Genus Bacillus ◽

Original Activity ◽

Bacterial Cultures ◽

Bacillus Genus

One hundred and fourteen bacterial cultures representing most of the species in the Bacillus genus were tested for the production of extracellular barley gum cytase. Assays were made on shake-flask cultures grown on a medium containing glucose and yeast extract. Although all the organisms had some enzymatic activity, certain strains of Bacillus subtilis gave the best yields of cytase. On a medium with asparagine as the sole nitrogen source even higher yields were obtained. The crude cytase preparations were stable and after freeze-drying most of the original activity remained.

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Cryptococcus Species Other Than Cryptococcus neoformans and Cryptococcus gattii: Are They Clinically Significant?

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa527 ◽

2020 ◽

Vol 7 (12) ◽

Author(s):

Edison J Cano ◽

Zachary A Yetmar ◽

Raymund R Razonable

Keyword(s):

Cryptococcus Neoformans ◽

Opportunistic Infections ◽

Descriptive Analysis ◽

Laboratory Data ◽

Invasive Disease ◽

Cryptococcus Gattii ◽

Cryptococcus Laurentii ◽

Cryptococcus Species ◽

Clinically Significant ◽

Cryptococcus Spp

Abstract Background Cryptococcus spp is a major cause of opportunistic infections in immunocompromised patients, primarily due to Cryptococcus neoformans and Cryptococcus gattii. There are occasional reports of other Cryptococcus species causing invasive human disease. However, their epidemiology and clinical significance are not fully defined. We sought to describe cases with cultures positive for Cryptococcus species other than C neoformans and C gattii. Methods A retrospective descriptive analysis of clinical and laboratory data of patients with cultures growing Cryptococcus species other than C neoformans and C gattii from November 2011 to February 2019 was performed. Three Mayo Clinic sites in Arizona, Florida, and Minnesota were included. Results From 176 cases with a culture growing Cryptococcus spp, 54 patients (30%) had a culture for Cryptococcus other than C neoformans and C gattii in the study time frame. The most common species were Cryptococcus magnus, Cryptococcus laurentii, and Cryptococcus ater. The organisms were isolated and identified in culture of bronchoalveolar lavage (11), skin (11), urine (7), oral (4), sinus (3), intraoperative soft tissue (3), sputum (2), synovial fluid (2), cerebrospinal fluid (2), and intravenous catheter (2), among others (7). Only 8 (15%) cases were considered to be potentially pathogenic, with 1 case of invasive disease. Antifungal treatment was fluconazole, itraconazole, and griseofulvin, for a mean systemic antifungal duration of 42 days. Conclusions This large series of patients with Cryptococcus spp other than C neoformans and C gattii suggests that these species rarely cause clinically significant infection in humans. Only 1 case of invasive disease was found.

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Molecular Characterization of the Von Willebrand Factor Type D Domain of Vitellogenin from Takifugu flavidus

Marine Drugs ◽

10.3390/md19040181 ◽

2021 ◽

Vol 19 (4) ◽

pp. 181

Author(s):

Kun Qiao ◽

Caiyun Jiang ◽

Min Xu ◽

Bei Chen ◽

Wenhui Qiu ◽

...

Keyword(s):

Amino Acids ◽

Von Willebrand Factor ◽

Molecular Mechanisms ◽

Protein Domain ◽

Type D ◽

Protein Toxin ◽

Factor Type ◽

Von Willebrand ◽

Willebrand Factor

The von Willebrand factor type D (VWD) domain in vitellogenin has recently been found to bind tetrodotoxin. The way in which this protein domain associates with tetrodotoxin and participates in transporting tetrodotoxin in vivo remains unclear. A cDNA fragment of the vitellogenin gene containing the VWD domain from pufferfish (Takifugu flavidus) (TfVWD) was cloned. Using in silico structural and docking analyses of the predicted protein, we determined that key amino acids (namely, Val115, ASP116, Val117, and Lys122) in TfVWD mediate its binding to tetrodotoxin, which was supported by in vitro surface plasmon resonance analysis. Moreover, incubating recombinant rTfVWD together with tetrodotoxin attenuated its toxicity in vivo, further supporting protein–toxin binding and indicating associated toxicity-neutralizing effects. Finally, the expression profiling of TfVWD across different tissues and developmental stages indicated that its distribution patterns mirrored those of tetrodotoxin, suggesting that TfVWD may be involved in tetrodotoxin transport in pufferfish. For the first time, this study reveals the amino acids that mediate the binding of TfVWD to tetrodotoxin and provides a basis for further exploration of the molecular mechanisms underlying the enrichment and transfer of tetrodotoxin in pufferfish.

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