Type: Research Essays
Sample donated: Valerie Cross
Last updated: September 17, 2019
TAXONOMY, PHYLOGENY AND BIOLOGY OF PURPUREOCILLIUM SPECIESIntroductionPurpureoicllium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel-Jones& Samson, comb. nov 2011, previously knownas Paecilomyces lilacinus,described by Samson 1974) is one of the representative and widelystudied species of this group. Thefungus Purpureocillium spp. isa saprophytic fungus under the family ophiocordycipitaceace of the orderHypocreales.
Different species of genus Paecilomyces have beenidentified such as Paecilimyces variotii and others, which used to beconsidered close relatives of P. lilacinum, but recent molecular and morphological study suggested that Paecilomyceslilacinus and Purpureocillium lilacinum belongs to different orders Eurotialesand Hpocreales respectively(Deng et al. 2012; Luangsa-Ard et al.2011). P.lilacinum is a ubiquitous, saprophytic, filamentous fungus with worldwide distributionaround and has wide range of habitats. This fungus has been isolated fromdifferent materials and soils such as grassland, forest, cultivated anduncultivated lands, desert, estuarine sediments and sewage and sludge, insects,nematodes and human beings. This fungus can degrade the grain quality, food andpapers, present in the laboratory air as a contaminant, and contaminate thecosmetic items such as skin creams, lotions and other clinical materials suchas plastic implants, catheters and others (Saberhagenet al 1997; Saghrouni et al.
2013). P. lilacinum is widely known as the nematophagous fungus, which has been detected mostly in the females of cyst and root knotnematode such as Meloidogyne species andother cyst nematodes and found to have antagonistic effect on nematodes. Thisfungus has also been detected in the rhizosphere of the cereals crops such aswheat and barley and also in decayed grape fruits (Denga et al.
2012; Rumbos etal 2006). Purpureocillium species can survive in wide range of thetemperature and pH. The maximum temperature ranges from 8 to 38 0Cand optimum temperature range from 26 to 30 0C(79 to 86 °F). Purpureocillium is very adaptable for its lifestylei.e. it may acts as entomopathogenic, mycoparasitic, saprophytic as well asnematophagous based on the availability. P.lilacinum produces a mycotoxin called Paecilotoxin, although itssignificance is unknown and its production varies according to its strains(Khan et al.
2003)Taxonomy and Phylogeny of PurpureocilliumspeciesScientific classification Kingdom:FungiDivision: AscomycotaClass: SordariomycetesOrder: HypocrealesFamily: OphiocordycipitaceaeGenus: PurpureocilliumSpecies:Purpureocilliumlilacinum The American mycologist Charles Thom, first described thisfungus in 1910, named as Penicillium. lilacinum, later in 1974 Robert A. Samson changed the name to Paecilomyces lilaciuns (Samson et al. 1974).In the 2000s decade the genus Paecilomyces was described as anon-monophyletic genera and Paecilomycesnostocoides, Isaria takamizusanensis and Nomuraea atypicola were the close relativesof Paecilomyeces lilacinus. Luangsa-ard et al. in 2011 again re-classified the genus and changed itsname to Purpureocillium lilacinumbased on the characteristic purple-colored conidia produced by this speciesalong with the morphological and molecular differences from Paecilomyceslilaciuns.
Previously,the Purpureocillium lilacinum used to be considered as fungi imperfectiand Duteromycetes because of lacking the proper sexual reproduction, but recentwhole genome sequencing and other phylogenetic analysis confirmed this fungusbelongs to ascomycetes (Fig. 1) (Prasad et al. 2015).
Many species of the Paecilomyceshave been described around the world and variation observed within the species(Fig. 2). Paecilomyces can be differentiated from Penicillium byits phialides, which taper into a long distinct neck and produces divergent ortangled conidial chains, while the Penicillium produces thesymmetrically branched phialides (Rumbos et al. 2006). Luangsa-Ard et al.
(2011) described bothmorphological and molecular characteristics of the new combination of P.lilacinum. Based on phylogenetic analysis of the partial 18S rRNA genes,the type species P. lilacinum belongs to Ophiocordycipitaceae,while another type species Paecilomyces variotii of Paecilomyces belongsto Trichocomaceae (Fig. 3) (Luangsa-Ard et al.
2011). ITS and partialtranslation elongation factor 1-? (TEF) genes were also used to identify the Penicillium adametzioides and P. lilacinum, morphologically bothspecies were found to be identical as the previous descriptions by Deng et al. (2012).The phylogenetic analysis of the 18s ribosomal RNA (rRNA) genes of these two-speciesrevealed that these two species are actually not exactly similar because theybelonged to different families. Paecilomyces adametzioides belongs to the family Trichocomaceae, whereas P.
lilacinus moved to the new family Ophiocordycipitaceae as a newgenus Purpureocillium and renamed as a P. lilacinum (Fig. 2).
Another phylogenetic analysis of5.8S rDNA and internal transcribed spacer (ITS1 and ITS2) sequences from fewentomogenous Paecilomyces speciessupported the polyphyly of the genus moreover; analysis showed the existencethese cryptic species in two orders such as Eurotiales and Hypocreales. Paecilomycesvariotii and Paecilomyces leycettanus belonged to Eurotiales same asother species such as Talaromyces and Thermoascus.
Another orderHypocreales, three major subgroups were observed and one of which included Paecilomycesvirdis, Paecilomyces penicillatus, Paecilomyces carneus andother two such as Paecilomyces lilacinusand Paecilomyces marquandii (Fig.2). However, the majority of the P. lilacinus and P.marquandii isolates formed a distinct and distantly related subgroup, whilethe other major subgroup contained Paecilomyces farinosus, Paecilomyces amoeneroseus, Paecilomyces fumosoroseus and Paecilomyces tenuipes (Inglis et al.2006; Luangsa-Ard et al. 2011). Due tothe difficulties and complexity in differentiation of Paecilomyces spp.
and P. lilacinum, MALDI–TOF MS (Matrix-assisted laser desorptionionization–time-of-flight mass spectrometry) technique was used toidentify these two species and this method was found to be a rapid, reliable,and logistically simplified alternative to sequence-based analysis for theroutine identification of Paecilomyces spp. and P. lilacinum (Barker et al. 2014).
Whole genomesequencing of the P. lilacinumprovided the genetic makeup of this fungus and determined the rightphylogenetic placement (Fig. 1; Table 1.). Whole genome nucleotide sequences ofnine species belonging to Hypocreales order were used to create thephylogenetic tree for P. lilacinum that provided the confirmation of theP. lilacinum as a different speciesfrom the Paecilomyces lilacinus underthe order Eurotiales (Prasad et al.
2015). Another new species named Pupureociliumlavendulum closely related to P. lilacinum was proposed by Perdomoet al. in 2012 by analyzing the ITS sequence of 37 clinical isolates from different origins and sources including otherreferences strains of P. lilacinum, Paecilomyces nostocoides and Nomuraeaatypicola, the new species was characterized by yellow diffusible pigmentwith subglobose or limoniform conidia (Perdomo et al. 2012).
Table 1. Genomic features of P. lilacinum(Adapted from Prasad et al. 2015) Features P. lilacinum Genome Size (Mb) 40.02 % GC content 58.
57% Predicted Proteins 13266 Avg. gene density (genes/mb) 303 Avg. gene length (bp) 1512 Repeat content 1.68 tRNAs 91 Secreted Proteins 1276 Secondary metabolites clusters 30 (SMURF), 46 (AntiSMASH) PHI genes 1953 Proteases 480 Morphology of PurpureocilliumlilacinumP. lilacinum produces moderately to fast growing mycelium colonies on MEAmedia (Fig. 2). It produces the conidiophores with floccose overgrowth ofaerial mycelium in it.
P. lilacinum produces purple colored conidia,which referred to its generic name Pupureocillium. The mycelium coloniesfirst appears as white colony and later on develop into pink and lilac then thesporulation starts.
The reverse color usually looks as purple or yellow. The fungus produces smooth walled hyalinevegetative hyphae of about 2.5 -4.0 µm wide. The conidiophores arise from submerged hyphae as mononematous stiffwith verticillate i.e.
phialides ovate to cylindrical having distinct neck,densely group together forming verticils of branches and cylindrical phialideswith or without very short neck. Conidia are produced as dry divergent chainswith straight to slightly curve or ellipsoidal to fusiform shaped with smoothto slightly roughened. This fungus does not produce chlamydosporesn and spores germinate in the suitable environmentalconditions such as temperature of 25 °C (77 °F) with enough moisture and nutrient available. Purpureocillium lilacinum as a human pathogenP. lilacinum is the one ofthe important cause of human diseases. This pathogen is associated with severaldiseases such as Chagas disease, immune system compromised for intraocular lensimplants, contaminant of antiseptic cream, tattoo- related skin infection andcavitary pulmonary disease (Jenifer et al.2011; Khan et al. 2012; Saghrouni et al.
2013; Trinhand Angarone 2016). The World Health Organization (WHO) has declared the Chagasdisease as one of the greatest scourges in South America and about 16-18millions of people are infected with this disease and more 100 millions ofpeople from 21 Latin American countries are at risk. For example in Argentina,Chagas disease is considered the most dangerous endemic arhropozoonosis with 2 millionsof people infected with Trypanosoma cruzi, thecausative agent of Chagas disease.
The presence of P. lilacinus was confirmed in Triatoma infestans Klug, vector of Chagas disease under phase contrast lightmicroscope from the all dead insect and fungus was re-isolated from insectcadavers (Marti et al. 2006; Gerardo et al.
2006). As Paecilomyces lilacinus was describedmore than a century ago as a fungus commonly found in soil, but in last decadesseveral reports have been published and confirming the fungus can be a causativeagent of many infectious diseases in man and other vertebrates. Several casesare described from the patients with compromised immune system or intraocularlens implants (Jenifer et al. 2011).
Other research results also suggested thatthe P. lilacinum can contaminatecosmetics items such as antiseptic creams and (skin) lotions, and otherneutralizing agent such as sodium bicarbonate solutions for artificial lenses,and can contaminate and colonized the medical materials such as catheters andplastic implants (Pettit et al., 1980; Orth et al., 1996; Itin et al., 1998). Atattoo-related skin infection was found to have association with the P.lilacinum in kidney transplant recipient and other similar reports has beendescribed as cutaneous infection inimmunocompetent patient (Saghrouni et al.
2013). P.lilacinum as a biocontrol agent for plant-parasiticnematodesThefungal order Hypocreales consists many fungal species, which are plantpathogens, insect-pathogens, nematode-pathogens, plant endophytes andmycoparasites.
The fungus Purpureocilliumlilacinum is widely known as a biological control agent against different plantparasitic nematodes, insects and pests (Fiedler et al. 2007; Parajuli et al. 2014). Purpureocillium lilacinum, previously named as Paecilomyceslilacinus.
These fungal species are known to produce a diversity ofsecondary metabolites and bio-actives, which acts as biological control agentfor nematode and insect pests. P.lilacinum produces a mycotoxin named as paecilotoxin, which is considered aneffective biological control agent against plant parasitic nematodes,especially economically important nematode species, Meloidogyne incognita (Bonants et al. 1995; Khan et al. 2004). Different research studiessuggested that nematode suppressive soil has a substantial presence ofnematophagous fungi such as P. lilacinum andPochonia chlamydosporia and others. Similar to other speciesin Hypocreales, P.
lilacinum has abroad host range and its various strains parasitize different species ofnematodes and insects. P. lilacinumis also reported to exercise parasitic or endophytic lifestyles in the presenceof a host organism such as nematodes, aphids and cotton plants. Strain251 of P. lilacinum, is one of widely used strains in plant parasiticnematode control that infects eggs and females of Meloidogyne spp. and causes death of the nematode embryos in 5 to 7days.
Improving suppression of Meloidogynespp. by Purpureocillium lilacinumstrain 251 tested in cotton, peanut, and maize. Strain 251 found to be moreeffective in peanut and cotton than in maize planting cover crops could also enhancethe effectiveness of P. lilacinum. (Parajuli et al. 2014). Besides thenematode control, P.
lilacinum can asa biological control agent of leafcutter ants in crops and plantations (Goffreet al. 2015). HYBDPL-04 strain of P.
lilacinum found to be highly effective for management of root-knotdisease of tomato under naturally infested field conditions. This isolatesfound to produce the maximum number of metabolites, which analyzed through high-pressureliquid chromatography (Singh et al. 2013). Cotton seeds infected withtwo entomopathogens B. bassiana and P.lilacinum showed the adverse effect on cotton aphid reproduction both inthe greenhouse and field experiment (Diana et al. 2014; Lopez et al.
2014). P. lilacium also improvesmangrove ecosystem by compensating the cupper stress by increasing theconcentration of cupper in the soil and improve the carbonate bound cupper inthe soil (Gong et al. 2017). Enzymes produced by PupureocilliumlilacinumP. lilacinum produces several enzymes, which act as a biological controlagent for nematodes, serine protease is a basic enzyme produced by this fungusthat is utilized against the biological activity of plant parasitic nematodesuch as Meloidogyne hapla (Bonants etal. 1995).
Proteases and chitinases are the other enzymes, which weaken thenematode eggs shell and prevent from penetration to plant cell and reduces thehatching of Meloidogyne javanicajuveniles (Khan et al. 2004). DiscussionPupureocillium is one of the commonly used nematophagous fungus under the family ophiocordycipitaceace.
Previously, Purpureocillium was described as Paecilimyces lilaciuns,but later several moophological, molecular, and phyologenetic analysis confirmthe fungus as a different group species as Pupureocillium, the namereferred as purple colored conidia. P. lilacium is a representative speciesunder the genus Purpureocillium, but additional species has been described forexample Pupureocilium lavendulum. This fungus is widelydistributed and detected from several material such as soils, sludge,cultivated and unclultivated land, females of nematodes and adaptable to variedenvironmental conditions. This fungus is highly adaptable to the situation andcan acts as entomopathogenic,mycoparasitic, saprophytic as well as nematophagous upon availability.
Ithas been used for managing plant parasitic nematode mainly cyst and root knotnematode. Besides nematode this fungus also been used to control other insect andpests. Besides its advantage as a control agent for nematodes and other pest,it also considered as a human pathogen. Several clinical cases has beendetected, where this pathogen found to be associated with the human diseases.
Chagasdisease, immunocompromised patent, tattoo-related skin infection, keratitisand, as a contaminant of cosmetics and medical utilities such as plasticimplants and catheters are some of the examples where the Purpureocilliumlilacium found to associated or directly involved to cause the disease.P. lilacinum has both the positive and negative aspects. Several research studiessuggest that this fungus can acts as effective biological control measures nematode,insect and pest crop plants, but this pathogen also becoming dangerous humanpathogens and found to be associated with several human diseases. It is veryimportant to investigate more about P.lilacinum as utilizing as a biological control agent for nematodes andinsects and its possible impacts on human beings and the environment. Furtherresearch are required for further application of this fungus as a biologicalcontrol agent for nematodes and insects. ReferencesBarker, A.
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