Cellular Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota and Deuteromycota. Phylum Chytridiomycota

life on earth can be divided in three different domains – the eukaryotic, prokaryotic
and archaea. Within these, further sub distinctions can be made, resulting in a
branched and complex annotation of life.  Fungi belong to the eukaryotic domain, in
which they constitute their own kingdom, besides the plant and animal kingdoms.
As other eukaryotic cells, fungi cells accommodate organelles and a true
nucleus, all contained within a membrane, while they differ by having a cell
wall consisting of chitin, as well as lacking chlorophyll. The general scheme
of a fungi is relatively simple. Composing of a main body, a mycelium, made up
by a branched network of tubes, hyphae. Through hyphae, nutrients are absorbed,
in which organic carbon, from either living or dead biological organisms,
function as the main energy source. Reproduction of fungi can occur in two separate,
yet connected, ways. Either reproduction takes place asexually, mainly through the
means of the release of small identical copies of parent fungi as spores, or
reproduction occurs sexually. Sexual reproduction varies between different
phylums and therefore a generic description does not make sense. Instead a
detailed description is integrated within the description of each phylum.

The fungi
kingdom can be subdivided in 5 different phyla, these are named Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota and Deuteromycota.

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Phylum Chytridiomycota
all fungi, which at some point in their life cycles exists as flagellated
swimming cells and these fungi are therefore, primarily, found in aquatic
environments. These fungi reproduce asexually when a zoospore, who are
uniflagellate asexual spores, lands on a substrate, after which a cell wall
forms around it, thus, creating a fungi body. Long threads, rhizoids, attach to
the substrate and through these nutrient is absorbed. After a period of
feeding, the fungi body is converted into a sporangium, a structure which
contains and subsequently releases zoospores. Sexual reproduction occurs by
fusing zoospores, thus creating a diploid zygote, which then hardens and
creates a meiosporangium. Later fusing of nuclei create meiospores, which can then
swim away and form a new fungi body. Fungi of this phyla are mostly harmless,
saprotrophic fungi, although a few pathogens such as Batrachochytrium dendrobatidis, which causes chytridiomycosis in amphibious animals
have been found.

Phylum Zygomycota clusters more than 1100 different species, mostly
saprotrophic soil fungi, who exploits nutrients by decomposing waste products,
such as rotten fruit. Their name, refers to their reproductive sexual
mechanism, as it forms a structure called zygosporangium, arising from the
conjugation between two compatible hyphae, with each hyphae stemming from a separate
organism.  After conjugation, a cell wall
is formed behind the fusing hyphae, which at this point are called gametangia.
Next to this, the wall separating the two hyphae is broken down, leading to
fusion of both hyphae’s cell components into one organism, except their nuclei,
which are still separate entities. Following this, their nuclei fuse and the
walls around the zygosporangium grows even harder and thicker than before – this
converts the sporangium to a zygospore. After a long resting period, meiosis occurs,
and the fused nuclei are divided into two separate recombinant nuclei.  These are then later integrated and released
as meiospores. Most Zygomycota are harmless to humans, although a few are
pathological causing a disease called mucormycose,
which arises when spores are inhaled from dusty environments. 

Fungi in the third
phyla, phylum Ascomycota, are the
most abundant phylum as more than 65.000 species belong here. Their trademark
is their structural component, the ascus, which is a sac-like unit, harboring
eight ascospores, in which sexual and asexual reproduction occurs. The formation
of this component arises when a spore lands on a suitable substrate, after
which a haploid mycelium is formed. From this, asexual structures can be
produced, or sexual structures, gametangia, can be formed. The female sexual
structure is called ascogonium, while the male sexual structure is an
antheridium.  Fusing of sexual structures
leads to formation of one organism with two separate nuclei, this is called an
ascogonius hypha. Fusing of nuclei, takes place at the tip of this hyphae,
creating a diploid ascus, who undergoes meiosis and thus produces 4 recombinant
haploid nuclei. Followed by a round of mitosis eight ascospores are formed,
which can then be released and the cycle repeats. Due to the sheer amount of
species, phylum Ascomycota, exert both a positive and negative effect on the
human condition. Beneficial species such as Penicillium
notatum and Saccharomyces cerevisiae
contribute to our health and or ability to produce beverages, while malign
effects are seen by species of the Aspergillus genus who can cause a respiratory
disease, decay food, synthetize carcinogenic toxins in nuts etc. The
Aspergillus genus will be investigated extensively later in this paper.

fourth phyla, Basidiomycata, are next
to Ascomycota the most abundant phyla with more than 30.000 separate species
and because of this abundance, their diversity is large and plentiful. This
phylum encompasses the largest and most complex fungi, in which most species share
a common structural component coined basidium. 
The basidium is a club shaped structure, in which meiosis takes place
and where basidiospores are synthesized, often located on fruiting bodies such
as mushrooms.

reproduce asexually by producing spores or by a mechanism called budding, in
which an extension of a cell is separated into its own cell. Sexual
reproduction happens when haploid hyphae meet and fuse, often followed by the
transfer of a nuclei from each parent hyphae to the other, which reproduces
mitotic, thus, creating a dikaryotic mycelium.  From dikaryotic mycelium a fruiting body
arises, by hyphae, who communicate and create different components. Some create
the stalk, other the gills of the fruiting body. The tips of the hyphae which
constitutes the gills is the basidium and when these swell, nuclei are fused
and a bit after 4 basidiospores are formed, which will then be ready to be
released. Basidiomycota play an important role in ecosystems, as they achieve
nutrient by breaking down decomposing organic material, unfortunately they also
break down wood, which have negative economical consequences.

The last phyla, phylum Glomerucyto, is a new addition to
the additional four phylae. These fungi live in close association with the
roots of trees. Their relationship is symbiotic in which the roots contribute
with carbohydrates and carbon, while the fungi stacks essential vitamins and
minerals which the plant can utilize. Glomeromycota do not reproduce sexually
and cannot sustain life without support from plant roots.

remaining fungi that do not fit in any of these phyla, belong to a sixth
informal phylum called phylum Deuteromycata. These fungi all reproduce solely
asexually are as individuals closer to other phyla but not close enough to be
considered a valid part of these. 


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