Fonticula

Fonticula
	Macro photograph of an F. alba colony radius growing on a plate.
Scientific classification
Domain:	Eukaryota
(unranked):	Opisthokonta
(unranked):	Holomycota
Class:	Cristidiscoidea
Order:	Fonticulida
Family:	Fonticulaceae
Genus:	Fonticula; Worley, Raper & Hohl 1979
Type species
	Fonticula alba; O’Kelly & Nerad 1999
Species
	F. alba;

Last updated April 16, 2024

Fonticula is a genus of cellular slime mold which forms a fruiting body in a volcano shape.^[1] As long ago as 1979 it has been known to not have a close relationship with either the Dictyosteliida or the Acrasidae, the two well-established groups of cellular slime molds.^[2] In 1979, Fonticula was made a new genus of its own due to the unique characteristics of its fruiting body, with only one species: Fonticula alba.^[2]

History and etymology

While working at the University of Wisconsin in 1979, Ann Worley, Kenneth Raper and Marianne Hohl discovered an organism that fit no recognized genus of the slime mold taxon Acrasiomycetes. At the time Acrasiomycetes could be divided into two classes: Acrasidae and Dictyostelidae. This classification was based on morphological characteristics, but it is now known that the two subgroups are not closely related.^[3] Moreover, F.alba did not truly fit into either of these subclasses but shared a few characteristics of both.^[2] Although F.alba shared characteristics of subclasses within Acrasiomycetes, Worley et al. (1979) were convinced that its best fit taxonomically would be in a new, undescribed family designated as Fonticulaceae, which would then contain the genus Fonticula. The new genus name Fonticula is a reference to the fruiting-body morphology: Fonti- from the Latin word Fons (fountain, "shape, form") and -cula, from Latin diminutive culus (little, "size").^[2]

Opisthokonta is an exceptionally diverse eukaryotic group, containing shared ancestry between fungi, animals and even a few protists (Brown et al., 2009). In 2009 it was concluded that the genus Fonticula is part of the unranked group Opisthokonta. Brown et al. (2009) sequenced nuclear encoded genes of Fonticula alba for phylogenetic analysis and concluded that the genus was a sister group to the filose amoebae in the genus Nuclearia and that the Fonticula and Nuclearia clade are sister groups to fungi.^{[ citation needed ]}

Description

Morphology and anatomy

The morphological characteristics of genus Fonticula are unlike those seen in slime mold subgroups Acrasidae or Dictyostelidae. Several studies have found that in its vegetative state, myxamoebae of F. alba are generally small and irregular in form, ranging from 8-12 x 6-10 μm in size.^[2]^[1] The myxamoebae have finger-like projections deemed as filose pseudopodia, which extent at the posterior or lateral ends of the cell.^[2] Worley et al. (1979) found that the myxamoebae had a distinguishable ectoplasm and endoplasm. The clear ectoplasm is on the outer edges, while the inner endoplasm is more granular. Vacuoles are also found in numerous digestion stages in actively feeding F. abla.^[2] These small vacuoles contain bacteria. In active feeding stages, there is a slime coat surrounding the myxamoeba to which bacteria sink onto.^[1] The ultrastructure of Fonticula also includes small contractile vacuoles, which are mainly deposited towards the posterior end of the cell.^[2] An ultrastructural feature that is shared between Fonticula and certain Acrasidae is mitochondria with discoid cristae.^[2] The golgi apparatus lends a helping hand in the fruiting stage in Fonticula as numerous dictyosomes are involved in the sorogenesis process.^[1] Cells in the genus are generally uninucleate, however there have been cases of some cells containing two or even three nuclei.^[2] The nucleus of F. alba cells have an inconspicuous nucleolus under the light microscope.^[2] The fruiting body of F. alba contains an unbranched sorocarp, which is composed of upright tapered stalks which apically bear a round source containing spores. Stalks range from 200-500 μm in length. The sori on the fruiting body are white, and roughly 200-350 μm in diameter. Spores are cystic in shape, and roughly 5.0-6.0 μm in diameter.^[2]

Phylogenetics

Multigene phylogenetic analysis was conducted in F. alba in 2009 which allowed it to be placed into Opisthokonta. The five nuclear encoded genes that were sequenced were: small subunit ribosomal RNA (SSU rRNA), actin, beta-tubulin, elongation factor 1-alpha (EF1-a) and heat shock protein 70 (HSP70). The study's results depicted that from 42 eukaryotic taxa, many alignments were made with a total of 2802 aligned sequences (Brown et al., 2009). Phylogenetic trees based on the molecular genetics sequenced in this study showed that the genus Fonticula was a sister taxon to the genus Nuclearia. Those two sister taxa as a clade are in turn a sister taxa to Fungi. Fonticula therefore represents the first evolution of an organism with a cellular slime mold-like morphology within the broad-group Opisthokonta (Brown et al., 2009); (Brown, 2010).

Another study done by Barlow et al. in 2014 traced the evolution of the five adaptor protein (AP) complexed in fungi, but also provided some insight onto Fonticula alba. The adaptor proteins investigated work in vesicular transport in eukaryotes, particularly in cargo-selection and coat-protein recruitment. The study found that F. alba had all five adaptor protein complexes present in its genome, whereas the kingdom Fungi only retained the first three adaptor protein complexes (Barlow et al., 2014). This study concluded that the last common ancestor of the sister groups Fungi, and Fonticula and Nuclearia (also known as the clade Holomycota) contained a complete set of all five adaptor protein complexes.

Life cycle

An amoeboid trophic phase alternating with an aggregating fruiting phase describes the life cycle of F. alba. Fruiting bodies are volcano-like structures that are unique to its genus.^[1] Commencing of the fruiting stage occurs when trophic amoeba halt their feeding, and dense aggregations begin to form (Deasey, 1982). Over time, an envelope of a mucus-like substance begins to surround the aggregated amoebae.^[2] The amoebae at the top of the aggregation begin to project upward, and a hyaline membrane is laid down onto the projection, as development occurs. Stalk material is secreted while the amoebae move upwards within the projection.

In early stages of orogenesis, the cells form a number of dictyosomes from the outer nuclear membrane in response to a certain stimuli.^[1] The dictyosomes aid in the accumulation and deposition of stalk material. The golgi apparatus in F. alba swells up, instead of having small vesicles pinch off is cristae, which is unique to the genus.^[1] The vesicles produce a thread-like material, within a mucous-matrix that lets the aggregated mound turn into a tapered stalk.^[2] The vesicles then release their internal contents via fusing with plasma membrane of the sorogenic cells. The material made within the vesicles is mostly assembled at the thick base of the stalk, and is thought to provide structural support. Cells are amoeboid during stalk formation.

As the sorocarp reaches max height, orogenic cells begin to depict differential shapes and thus different functions. Amoeboid cells remain near the base, continuously producing stalk material through their numerous dictyosomes during spore formation. These cells continue producing stalk material even when spores have been released.^[1] Cystic cells are above the amoeboid cells, these cells are preparing to flourish into spores and thus have less dictyosomes, known as "pre-spores".^[1]

The ultrastructural comparison between the amoeboid cells and pre-spores is quite evident. The pre-spores have less dictyosomes which tend to be flattened. As the number of dictyosomes decreases, the cytoplasm takes up more room within the cell and the cell adapts a more round shape (Deasey, 1982). There is also a difference in the plasma membrane of amoeboid orogenic cells and pre-spore cells. The pre-spore cells plasma membrane appears to be invaginated, whilst the amoeboid cells PM looks smooth (Deasey, 1982). Elliptical cells, located in the upper neck of the sorocarp are a little further along into spore-development than the cyst cells. These cells lack dictyosomes, are thick-walled and thought to increase pressure within the neck of the stalk.^[1] As pressure increases, the encysted cells will then come up from the apex and come together and form a large ball called the sorus.^[2] The majority of the cells within the source have successfully developed into spores. When the sorus is developed, the neck of the fruiting body is almost fully lacking in sorogenis cells. Amoeboid cells remain at the base of the sorocarp.^[1] Spores of F. alba release and flow as the stalk collapses as time goes on. The optimal pH for growth and fruiting-body development for Fonticula alba is a substrate with a near neutral pH. A lower pH may result in a poorly developed fruiting structure.^[2]

Culturing techniques

The vegetative stage in F. alba consists of unicellular, myxamoeba that feed on bacterial cells.^[2]F. alba grows with Klebsiella pneumoniae upon a nutrient agar.^[2] In the study done by Worley et al (1979), Fonticula alba was cultured on a tryptone-glucose-yeast-extract agar.

Worley et al. (1979), also investigated the effect of substrate concentration on Fonticula alba cell growth and sorocarp formation. They found that on a more concentrated substrate, cell growth advanced more quickly and normal sorocarp formation followed. On less concentrated media, they found opposite results.

F. alba was also cultured with different strains of bacteria, to determine if other bacterial species could serve as a nutrient. The agar was streaked with different bacteria such as Bacillus megaterium, Serratia marcescens, Pseudomonas fluorescens, Micrococcus luteus, and Escherichia coli. The strains with B.megaterium, S.marcescens, and P.fluorescens sorocarps did develop, but lesser and later than normal. In the strains with M.luteus it was found that no sorocarps or myxamoebae grew. The strain with E. coli did show adequate growth and fruiting. However, compared to K.pneumoniae, the sorocarps that grew with E. coli were smaller in size.^[2]

F. alba grows at an optimal temperature range of 25-28 degrees celsius. However, it tends to grow at a broad range of 16-37 degrees celsius. Studies have shown that it does not grow at a lower bracket 10 degrees celsius or a higher bracket of 40 degrees celsius.^[2]

List of species

The genus Fonticula contains a sole species named Fonticula alba.

Related Research Articles

A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms which are more formally characterized.

The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages.

Nucleariida is a group of amoebae with filose pseudopods, known mostly from soils and freshwater. They are distinguished from the superficially similar vampyrellids mainly by having mitochondria with discoid cristae, in the absence of superficial granules, and in the way they consume food.

Slime mold or slime mould is an informal name given to a polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are microscopic; those in the Myxogastria form larger plasmodial slime molds visible to the naked eye. The slime mold life cycle includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic multicellular or multinucleate fruiting bodies that may be formed through aggregation or fusion; aggregation is driven by chemical signals called acrasins. Slime molds contribute to the decomposition of dead vegetation; some are parasitic.

The dictyostelids or cellular slime molds are a group of slime molds or social amoebae.

Dictyostelium is a genus of single- and multi-celled eukaryotic, phagotrophic bacterivores. Though they are Protista and in no way fungal, they traditionally are known as "slime molds". They are present in most terrestrial ecosystems as a normal and often abundant component of the soil microflora, and play an important role in the maintenance of balanced bacterial populations in soils.

Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In traditional classification schemes, Amoebozoa is usually ranked as a phylum within either the kingdom Protista or the kingdom Protozoa. In the classification favored by the International Society of Protistologists, it is retained as an unranked "supergroup" within Eukaryota. Molecular genetic analysis supports Amoebozoa as a monophyletic clade. Modern studies of eukaryotic phylogenetic trees identify it as the sister group to Opisthokonta, another major clade which contains both fungi and animals as well as several other clades comprising some 300 species of unicellular eukaryotes. Amoebozoa and Opisthokonta are sometimes grouped together in a high-level taxon, variously named Unikonta, Amorphea or Opimoda.

The opisthokonts are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and Breviata comprise the larger clade Obazoa.

Cristidiscoidea or Nucleariae is a proposed basal holomycota clade in which Fonticula and Nucleariida emerged, as sister of the fungi. Since it is close to the divergence between the main lineages of fungi and animals, the study of Cristidiscoidea can provide crucial information on the divergent lifestyles of these groups and the evolution of opisthokonts and slime mold multicellularity. The holomycota tree is following Tedersoo et al.

The family Acrasidae is a family of slime molds which belongs to the excavate group Percolozoa. The name element acrasio- comes from the Greek akrasia, meaning "acting against one's judgement". This group consists of cellular slime molds.

Dictyostelium discoideum is a species of soil-dwelling amoeba belonging to the phylum Amoebozoa, infraphylum Mycetozoa. Commonly referred to as slime mold, D. discoideum is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime. Its unique asexual life cycle consists of four stages: vegetative, aggregation, migration, and culmination. The life cycle of D. discoideum is relatively short, which allows for timely viewing of all stages. The cells involved in the life cycle undergo movement, chemical signaling, and development, which are applicable to human cancer research. The simplicity of its life cycle makes D. discoideum a valuable model organism to study genetic, cellular, and biochemical processes in other organisms.

Amoeba is a genus of single-celled amoeboids in the family Amoebidae. The type species of the genus is Amoeba proteus, a common freshwater organism, widely studied in classrooms and laboratories.

Protosteliomycetes/Protosteliales (ICBN) or Protostelea/Protostelia/Protosteliida (ICZN) is a grouping of slime molds from the phylum Mycetozoa. The name can vary depending upon the taxon used. Other names include Protostelea, Protostelia, and Protostelida. When not implying a specific level of classification, the term protostelid or protosteloid amoeba is sometimes used.

Trichiales is an order of slime moulds in the phylum Amoebozoa. Trichiales is one of five orders in the group Myxomycetes, or the true plasmodial slime molds. It is also currently categorized under the superorder Lucisporidia with its sister group, Liceales. The order was first described by Thomas MacBride in 1922, and has retained the same name and status as a defined order in present phylogeny. In the plasmodium form, members of Trichiales lack a columella but have a well-developed capillitium for spore dispersal. The shape and details of the capillitium are used to define families within the order. Spores are brightly coloured, ranging from clear, white and yellow to pink and red-brown tones. The order currently has 4 families, 14 genera and 174 species. Recent molecular research has shown that while Trichiales probably represents a true taxonomic group, its sister group Liceales is likely paraphyletic, and it has been suggested that several genera from the Liceales should be reclassified under Trichiales instead.

Holomycota or Nucletmycea are a basal Opisthokont clade as sister of the Holozoa. It consists of the Cristidiscoidea and the kingdom Fungi. The position of nucleariids, unicellular free-living phagotrophic amoebae, as the earliest lineage of Holomycota suggests that animals and fungi independently acquired complex multicellularity from a common unicellular ancestor and that the osmotrophic lifestyle was originated later in the divergence of this eukaryotic lineage. Opisthosporidians is a recently proposed taxonomic group that includes aphelids, Microsporidia and Cryptomycota, three groups of endoparasites.

A sorocarp is the fruiting body characteristic of certain cellular slime moulds. Each sorocarp consists of both a sorophore (stalk) and a sorus. Sorocarps release spores.

Polysphondylium pallidum is a species of cellular slime mould, a member of the phylum Mycetozoa.

An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.

Parvularia atlantis is a filopodiated amoeba which was isolated from a lake in Atlanta and deposited in the American Type Culture Collection (ATCC) under the name Nuclearia sp. ATCC 50694 on 1997 by TK Sawyer. It was classified under the genus Nuclearia and morphologically resembles to Nuclearia species, although it is smaller. Later it was determined that it phylogenetically belongs to a new nucleariid lineage., distantly related to Nuclearia and Fonticula genera – the other two previously described nucleriid genera.

Hemitrichia is a genus of slime molds, of the family Trichiidae, found within the order Trichiida. It was first described by Josef Rostafinski in 1873 and remains a well-defined genus of the slime molds. Hemitrichia species exhibit either plasmodiocarp or sporangium fruiting bodies, both of which are well-known and recognizable slime molds seen on multiple continents. The genus includes Hemtrichia serpula, known as the pretzel slime mold, an iconic and widespread species that has been used to examine speciation in slime molds.

References

1 2 3 4 5 6 7 8 9 10 11 Mary C. Deasey and Lindsay S. Olive (31 July 1981), "Role of Golgi Apparatus in Sorogenesis by the Cellular Slime Mold Fonticula alba", Science, 213 (4507): 561–563, Bibcode:1981Sci...213..561D, doi:10.1126/science.213.4507.561, PMID 17794844
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Ann C. Worley, Kenneth B. Raper and Marianne Hohl (July–August 1979), "Fonticula alba: A New Cellular Slime Mold (Acrasiomycetes)", Mycologia, 71 (4): 746–760, doi:10.2307/3759186, JSTOR 3759186
↑ Matthew W. Brown, Jeffrey Silberman, and Frederick W. Spiegel (May 2012), "A contemporary evaluation of the acrasids (Acrasidae, Heterolobosea, Excavata)", European Journal of Protistology, 48 (2): 103–123, doi:10.1016/j.ejop.2011.10.001, JSTOR 3759186, PMID 22154141 {{citation}}: CS1 maint: multiple names: authors list (link)