1. Microbiology
Specialty 241 “Hotel and Restaurant Business”
Topic 1. GENERAL MICROBIOLOGY
Theme 1 “Basic of morphology and systematic of
microorganisms. Fungi. Yeasts”
Stabnikov Viktor, PhD
NATIONAL UNIVERSITY OF FOOD
TECHNOLOGIES
2. Fungi are more high-organized organisms what bacteria. On the type
of cell they belong to eukaryotes.
All eukaryotic cells have the following:
A nucleus
Genetic material
A plasma membrane
Ribosomes
Cytoplasm, including the cytoskeleton
Most eukaryotic cells also have other
membrane-bound internal structures
called organelles. Organelles include:
Mitochondria
Golgi bodies
Lysosomes
Endoplasmic reticulum
Vesicles
3. The nucleus stores all the
information a cell needs to grow,
reproduce, and function. This
information is contained in long
but thin molecules of
deoxyribonucleic acid (DNA).
The nucleus also contains a small,
round body called a nucleolus.
The cell nucleus is a double
membrane‐bound organelle
that contains the genetic
information of the cell packaged
in the form of chromatin.
The nucleus also contains a liquid called nucleoplasm.
The nuclear double membrane, called the nuclear envelope, controls the cell's
growth and reproduction. It completely separates the nucleus from the rest of
the cell. Nuclear pores are large protein complexes that cross
the nuclear envelope.
4. Mitochondria are often called
the powerhouses or energy
factories of the cell. Their job
is to make a steady supply of
adenosine triphosphate (ATP),
the cell’s main energy-carrying
molecule.
Mitochondria are oval-shaped
and have two membranes: an
outer one, surrounding the
whole organelle, and an inner
one, with many inward
protrusions called cristae that
increase surface area.
The space between the membranes is called the intermembrane space,
and the compartment enclosed by the inner membrane is called
the mitochondrial matrix. The matrix contains mitochondrial DNA and
ribosomes.
5. The endoplasmic reticulum is composed of a group of interconnected
sac-like structures called tubules. These tubules collectively modify and
produce the proteins and lipids. It is a complex and large structure in the
cytoplasm and spans between the cell membrane and the nucleus. The
endoplasmic reticulum is classified into two types, rough endoplasmic
reticulum (Rough ER) and smooth endoplasmic reticulum (smooth ER).
Rough endoplasmic reticulum is the
site of protein synthesis.
Smooth endoplasmic reticulum is the
site of production of lipids.
6. Golgi apparatus, also called Golgi body, membrane-
bound organelle of eukaryotic cells that is made up of a series of stacked
pouches called cisternae. The Golgi apparatus functions as a factory in
which proteins received from the ER are further processed and sorted for
transport to their eventual destinations: lysosomes, the plasma membrane,
or secretion. It is located in the cytoplasm next to the endoplasmic
reticulum and near the cell nucleus.
7. Lysosome is responsible for the
digestion of macromolecules, old cell
parts, and microorganisms.
Lysosomes contain a wide variety of
hydrolytic enzymes (acid hydrolases)
that break down macromolecules
such as nucleic acids, proteins,
and polysaccharides
Additionally, eukaryotic cells have
ribosomes (with diameter around 20
nm) which translate genetic information
into proteins
8. The cytoskeleton is a highly dynamic network of filamentous proteins.
The cytoskeleton found within eukaryotic cells provides structural support to the
cells.
Elements of cytoskeletons are stained in red and
green colors, and the nucleus – in blue.
All organelles are placed in cytoplasm, the jelly-like fluid that fills a cell.
It is made up of mostly water and salt. Cytoplasm is present within the cell
membrane of all cell types and contains all organelles and cell parts.
Cytoplasm has various functions in the cell. Cytoplasm contains enzymes
which are responsible for breaking down waste and also aid in metabolic
activity. Cytoplasm is responsible for giving a cell its shape. It helps to fill
out the cell and keeps organelles in their place.
9. Vacuole is an important organelle.
They store food and water as well as
waste material before it is transported
out of the cell. Vacuole's also provide
turgor pressure against the cell.
Plant’s vacuole
Eukaryotic cell is surrounded with cell wall. The cell wall is the rigid, semi-
permeable protective layer found in some cell types. The cell wall is an
extracellular structure of cells that maintains cell's shape and protects cell
from mechanical damage.
Cytoplasmic inclusions are temporary structures that accumulate in
the cytoplasm of certain cells . Examples: lipids, glycogen, crystals,
pigment, or byproducts of metabolism are inclusions.
10. Eukaryotic cells have a plasma membrane, a phospholipid bilayer with
embedded proteins that separates the internal contents of the cell from its
surrounding environment. The plasma membrane controls the passage of
organic molecules, ions, water, and oxygen into and out of the cell. Wastes
(such as carbon dioxide and ammonia) also leave the cell by passing through
the plasma membrane, usually with some help of protein transporters.
11. Fungi
are a group of eukaryotic microorganisms. They are nonchlorophyllous
organisms that absorb nutrients from dead or living organic matter, have cell
walls composed of chitin, and store excess energy as glycogen.
Most fungi produce a mycelium composed of hyphae some of which extend
into the air while others penetrate the substrate on which they grow. Hyphae
branch and extend via tip elongation, although some groups (like yeasts)
consist only of individual cells. Hyphae (singular, hypha) are tube-like
filaments with either single multinucleate cells that lack septa (cross-walls)
separating nuclei, or many septate cells containing one, two, or more nuclei.
12. Mycelium of fungi Penicillium on
nutrient medium in Petri dish
Mycelium of fungi Rhizopus on nutrient
medium in Petri dish
Mycelium is the vegetative part of a fungus colony, consisting of a mass of
branching, thread-like hyphae. Fungal colonies composed of mycelium are
found in and on soil and many other substrates. At a certain stage it
produces spores, directly or through special fruiting bodies.
13. Hyphae that have walls between the cells are called septate hyphae. Septate hyphae
have dividers between the cells, called septa. The septa have openings called pores
between the cells, to allow the flow of cytoplasm and nutrients throughout the
mycelium.
Hyphae that lack walls and cell membranes between the cells are called nonseptate
or coenocytic hyphae. Non-septate hyphae form one long cell with many nuclei.
They are the more primitive form of hyphae.
Most fungi with coenocytic hyphae belong to the class Zygomycetes.
In contrast to molds, yeasts are unicellular fungi. The budding yeasts reproduce
asexually by budding off a smaller daughter cell; the resulting cells may sometimes
stick together as a short chain or pseudohypha.
14. Reproduction in Fungi: Vegetative, Asexual and Sexual
Methods
Vegetative reproduction: The most common method of vegetative
reproduction is fragmentation. The hypha breaks up into small fragments
accidentally or otherwise. Each fragment develops into a new individual. In
addition to above-mentioned common method of vegetative reproduction
the fungi reproduced vegetatively by other means, such as fission or
budding, etc. In fission, the cell constricts in the centre and divides into two
giving rise to new individuals.
15. Asexual reproduction:
Almost all fungi reproduce asexually by producing spores.
Asexual reproduction involves no union of cells or nuclei of cells.
Fungi reproducing asexually by means of sporangia.
The spores produced inside the sporangia are termed the endogenous spores
and the spores developing exogenously on the terminal ends of sporophores
(a fungus hypha specialized to bear spores) are called the exogenous spores.
Sporangiospores are spores that are produced in a sporangium (plural:
sporangia). A sporangium in fungi is simply a cell
containing spores. Sporangiospores may be motile or non-motile.
16. For example, fungi of order Mucorales make the asexual spores inside sporangia. Spore
production in the sporangia occur when the cytoplasm and the nuclei are divided by
newly cell walls to form spores. Sporangiophores are aerial hyphae, normally
unbranched that form sporangium filled with spores at their tip.
Mucor fungi are characterized by a body of branching mycelia composed of three types
of hyphae: stolons, rhizoids, and sporangiophores. Stolon – a special horizontal branch
serving to propagate the organism. Rhizoid, a short, thin filament that anchors the
growing body of the organism to a substratum and that is capable of absorbing
nutrients.
17. In some fungi the spores are not formed inside a sporangium. They are born
freely on the tips of special branches called conidiophores. The spores thus
formed are called as conidia. Conidia are always non-motile .
Aspergillus fungi : conidia are arranged in chains at the end of conidiophore.
Conidiophore is unbrached and contains vesicle and the end. Vesicle gives rise
to metulae and phialides that produce chains of conidia.
18. Mycelium of Penicillium fungi consists of branched and septate hyphae
composed of thin-walled cells containing one to many nuclei. Each septum
has a central pore, through which cytoplasm can flow.
The conidiophore may be unbranched or branched. Each sterigmata
develops at its tip a number of conidia arranged basipetally (younger one
near the mother and older one away from it). After maturation, the conidia
get detached and are dispersed by wind.
19. Sexual reproduction, an important source of genetic variability, allows
the fungus to adapt to new environments.
Sexual reproduction in the fungi consists of three sequential stages:
plasmogamy, karyogamy, and meiosis.
Pasmogamy is a stage, in which the cytoplasm of two parent cells fuses
together without the fusion of nuclei, effectively bringing two nuclei close
together in the same cell. The cell formed by karyogamy is called the zygote.
This state is followed by karyogamy, where the two nuclei fuse together and
then undergo meiosis to produce spores.
20. Classification of fungi
Fungi are usually classified according to biological taxonomy based upon the type of
hypha, spore, and reproduction. There are five classes of fungi.
The short description of these classes and some representatives of them will be shown
below.
Class Chytridiomycetes. A class of mostly aquatic fungi, single-celled structure, true
mycelium is lacking, sometime cell wall can be absent. Reproduction is going by mostly
asexually which are formed in sporangia. The class Chytridiomycetes contains fungi that
cause diseases in plants.
Potato cancer, the disease is caused by the fungus Synchytrium endobioticum, and this
organism is considered to be the most important world-wide quarantine plant pathogen
of cultivated potato.
Olpidium brass is a dangerous parasitic in the roots of cabbage.
Potato cancer
21. Class Phycomycetes.
Phycomycetes are fungi with an unicellular, non-septate mycelium (500 species). The
spores (endospores) an enclosed in special sporangia. A reproduction is sexual and
asexual. Asexual reproduction is going by spores producing the sporangia.
The plant pathogen Phytophthora infestans infected plants, such as tomato and potato.
Plasmopara viticolа infects all green parts of the host plant, the causal agent of
grapevine downy mildew.
22. Fungi Мисоr has a worldwide distribution. Mucor can spoil food products and
cause gastrointestinal illness in consumers and may pose a particular risk to
immunocompromised patients. It can infect bakery products, fruits and vegetables,
grow on the walls of storehouse facilities.
Some species of Mucor have been used in the production of alcohol in Asia and Africa.
23. Class Ascomycetes is a large class of higher fungi. It includes 35000 species.
They have a multicellular mycelium. The septal walls have septal pores which
provide cytoplasmic continuity throughout the individual hyphae. Under appropriate
conditions, nuclei may also migrate between septal compartments through the septal
pores.
The Ascomycetes reproduce sexually by means of ascospores (spores which develop
in spherical spore cases), asci—ascus (Gr. askos—sac) and asexually by conidia
(exospores ).
This class include yeasts also.
Blue-green, pink, and brown Ascomycetes molds cause food to spoil.
Certain Aspergillus species contaminate house dust ad cause allergies and respiratory
disease. Aspergillus species also produce dangerous chemicals called aflatoxins. The
aflatoxins from contaminated foods cause damage to nervous system.
Some representatives of class Aspergillus have a commercial use. Aspergillus niger is
used for the industrial production of food processing enzymes and metabolites such
as organic acids, mainly citric acid.
24. Aspergillus niger causes several diseases including black mold.
Aspergillus is mold that commonly grows
on bread, some strains of which can develop
dangerous mycotoxins.
25. Aspergillus niger is used for production of citric acid, Aspergillus oryzae for the
production of national Japanese alcohol drink sake.
Aspergillus is used for production of commercial enzymes including α-amylase, starch-
converting enzyme which is used in the production of maltodextrin, modified starches,
or glucose and fructose syrups. Amylases from Aspergillus oryzae are commonly used as
baking additives to prevent staling in the baking industry.
Amylases produced by fungi are also used in the production of washing powder.
26. The genus Penicillium belongs to the class Ascomycetes. The mycelium and
conidiophore are multicellular. The name Penicillium comes from the word
"brush“ because the fruiting body is in the shape of a brush. Many-branched
conidiophores sprout on the mycelia, bearing individually
constricted conidiospores. Conidia are round and unicellular. Glucans are
common in the cell walls of Penicillium species
27. Penicillium fungi are of major importance in the natural environment as
well as food and drug production. Some members of the genus produce
antibiotic penicillin, which kills or stops the growth of certain kinds of
bacteria. Other species are used in cheese making for production of blue
cheese: camemberti, brie, roquefort.
Species of Penicillium serve in the production of enzymes and other
organic acids.
Cheese Roquefort
Penicillium fungi produce antibiotics
penicillin and griseofulvin.
28. Penicillium species contaminate a wide variety of foods and are capable of
growing at refrigeration temperatures. Thus they often spoil refrigerated
foods, especially cheese. They can grow on grains, breads, cakes, fruits,
preserves, cured and aged hams and sausages. This spoilage brings with it
the potential for mycotoxin production.
29. Truffle, edible fungi , considered as a food delicacy, are
ascomycetes. Truffles are a delicacy in many cuisines, but finding them
deep in the forest isn't easy. Truffles are harvested in Europe with the aid of
female pigs or truffle dogs, which are able to detect the strong smell of
mature truffles underneath the surface of the ground.
The Italian white truffle is considered to be superior in smell and taste to the
French black truffle.
30. Class Basidiomycetes contains about 30,000 described species. This fungal
group is best known for the production of large fruit bodies such as the
mushrooms. The fungi of this group are characterized by the production of
spores known as basidiospores, whish are formed as a result of sexual process.
Humans widely use for Basidiomycetes. Mushrooms, both cultivated and wild,
are eaten in many countries. However, some Basidiomycota produce deadly
toxins.
Cantharellus
Aspen mushrooms
Boletus edulis
31. Many basidiomycetes fungi are used as food and are cultivated in a large-
scale for marketing:
Сhampignons (Agaricus bisporus )
The shiitake (Lentinus edodes) is an edible mushroom native to East Asia,
which iscultivated and consumed in many Asian countries. It is considered a
medicinal mushroom in some forms of traditional medicine.
Oyster mushroom (Pleurotus ostreatus)
32. Class of Deuteromycetes or Fungi Imperfecti includes species in which
sexual reproduction has never been observed. There are approximately
17,000 species in this class. Most species have a well-developed, septate
mycelium with distinct conidiophores but some have a unicellular thallus.
The members reproduce by means of conidia. Conidia may be spherical,
ovoid, elongated , star-shaped and so on. They may be one-celled to many-
celled, with either transverse septa or both transverse and longitudinal
septa. In addition, conidia may be hyaline or colored. These conidial
characteristics are the basis for the artificial classification. Members of
this group are mostly saprobes, but some are parasitic on plants and
animals, including man.
Fusarium is representative of this class. Mycelium is branched, conidia are
crescent shaped, multi-septate (3-5 septa).
33. Fusarium graminearum causing intoxication in human (drunken bread), and
Fusarium sporotrichioides causing intoxication in man and domestic animals
who had eaten the grain crops which had remained in the fields during the
winter.
Fusarious contaminated grain
34. Oidium gets its name from the Greek word for small egg: oidion.
Oidium species are plant pathogens causing powdery mildew diseases
found on leaves, stems, flowers and fruits of living higher plants.
Oidium occurs singly or in short chains of 3-6, single-celled asexual
spores produced by fragmentation of fungal filaments (hyphae).
35. Oidium are plant pathogens causing different forms of powdery mildew, can spoil milk
and milk products.
36. Yeasts
Yeasts are eukaryotic, single-celled nonmobile microorganisms belonging
to the class Ascomycetes. Some species have the ability to develop strings
of connected budding cells known as false hyphae. Yeasts are very
common in the environment, and are often isolated from sugar-rich
materials.
Fermentation of sugars by yeast is the oldest and largest application of
this technology. It can be used to make bread and alcoholic drinks such as
beer and wine .
However, uncontrolled growth of yeasts within food products such as cheeses,
meats, or by the fermentation of sugars in juices or jams led to their spoilage.
37. Shape and structure of the yeast’s cell
The shape of yeast cells may be spherical,
globous, ellipsoidal, cylindrical with rounded ends,
rectangular, pear-shaped, lemon-shaped, so on. The
diameter of a spherical cell may vary from 2 to 10
μm. The length of cylindrical cells is often 20–
30 μm and, in some cases, even greater.
Yeasts are eukaryotes, structure of their cell is similar
to the structure of fungi’s cell. Cell wall of yeasts
contain hemicelluloses, small quantities of protein,
lipids, and chitin. In cytoplasm of yeasts cell there are
nucleolus with nucleolus membrane, endoplasmic
reticulum, Golgi bodies, lysosomes, ribosomes,
mitochondria and vacuoles with store nutrient
substances, such as drops of lipids, volutin (reserve of
polyphosphates), glycogen (reserve of
polysaccharides). There are no chloroplasts in yeast
cells.
38. Reproduction of yeasts. Yeasts, like all fungi, may have asexual and
sexual reproductive cycles. The most common mode of vegetative growth
in yeast is asexual reproduction by budding. A small bud, or daughter cell, is
formed on the parent cell. The nucleus of the parent cell splits into a daughter
nucleus and migrates altogether with cytoplasm and other cell structures into
the daughter cell. The bud continues to grow until it separates from the parent
cell leaving a bud scar. The daughter cell produced during the budding process
is generally smaller than the mother cell. Time of budding is approximately 2
hours.
39. A large number of buds are developed without being detached from one
another resulting in the formation of branched or unbranched chains of
cells constituting the pseudomycelium. The cells in chains for
pseudomycelium are loosely joined together. Sooner or later, however, the
chains break into their constituent cells.
In some yeasts when the food is exhausted, or
when there is danger of desiccation, spores are
formed from the mother cells. In the process of
spore formation the protoplasm divides,
usually into four portions, each of which
becomes surrounded with a comparatively
thick wall. Thus four thick-walled spores
known as endospores are formed.
40. Some yeasts, for example Schizosaccharomyces pombe, reproduce
by fission instead of budding, creating two identically sized daughter cells.
During reproduction of fission yeasts the parent cell elongates (B), the
nucleus divides into two daughter nuclei, and gradually a transverse
partition wall is laid down near the middle starting from periphery to the
centre dividing the mother cell into two daughter cells (C and D).
41. A lot of yeasts are able to reproduce by sexual process forming spores.
Formation of spores is going under environmentally stressful conditions, for
example lack of nutrients. S. cerevisiae will undergo meiosis and form haploid
spores that are released when environmental conditions improve.
Sexual reproduction takes place by the union of two cells more often similar in
size but sometimes they may be dissimilar in appearance, and by the
development of short protuberances which unite to form a conjugation tube.
This is followed by the dissolution of intervening walls and nuclear fusion
which takes place in the conjugation tube. Gradually the two cells along with
the conjugation tube form the zygote cell. The zygote cell develops into an
ascus. The diploid zygotic nucleus undergoes three divisions, of which the first
one is meiotic, producing eight haploid nuclei. Each nucleus with cytoplasm
develops into an ascospore and the ascus contains eight ascospores. The
ascospores liberate by the breaking down of the ascus wall. They now behave
as somatic cells.
.
42. The main representatives of yeasts.
Systematic distribution of yeasts on families, genera and species is based on the
type of their reproduction, physiology, biochemical, morphological and genetic
abilities.
Many members of the genus Saccharomyces are considered very important in
food production, especially species S. cerevisiae. Cells of S. cerevisiae are
unicellular, globose, and ellipsoid to elongate in shape. It used for production of
alcohol, beer, kvass, bakery production.
Saccharomyces vini, S. ellipsoideus have cells of elliptic shape. This species are used in
wine production. Each type of wine is produced using specific strain of yeasts.
All species of the genus Saccharomyces under uncontrolled growth on the food
products containing sugar cause their spoilage: fermentation and souring.
43. Two other important yeasts genera for practice are Torulopsis and Candida.
The yeasts Torulopsis kefir are used for production of kefir and horse milk.
44. Yeasts Сandida: prolonged cells of cylindrical
shape, can form pseudomycelium. These yeasts
can be cause of spoilage of beer, wine, bakery
yeasts, soft drinks and other sugary food
products.
Candidiasis is a infection caused by
yeasts that belong to the genus Candida.
There are over 20 species of Candida
yeasts that can cause infection in humans,
the most common of which is Candida
albicans. Candidiasis can develop in the
mouth or throat.
45. Biomass of yeasts is rich in protein, its content could be so high as 66%.
Agricultural wastes, food processing wastes, or wood hydrolysates could be
used for yeasts growth. Single cell protein may be used as animals feeds.
