Microbiology - Algae Algae is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Algae are sometimes considered plants and sometimes considered "protists" (a grab-bag category of generally distantly related organisms that are grouped on the basis of not being animals, plants, fungi, bacteria, or archaeans).

1. TOPIC : ALGAE

2. TABLE OF CONTENTS
1.Algae - Introduction
2.General characteristics
3.Classification of Algae
4.Reproduction in Algae
5.Thallus and its structure
6.Mode of nutrition
7.Distribution of Algae
8.Benefits of Algae

3. ALGAE
Algae are a group of predominantly aquatic, photosynthetic, and nucleus-
bearing organisms that lack the true roots, stems, leaves, and
specialized multicellular reproductive structures of plants.
Algae represent ancient plants comprising different evolutions such as
photoautotrophic organisms. Algae are thallophytic and have vegetative
bodies which are not organized in roots and leafy stems. Many algae are
living in solitary cells, colonies, filaments, or primitive vegetation
bodies and do not have a vascular system. The algae are cryptogams that
propagate with the hidden reproductive strategies. Following a
conception of subdivision of living organisms into five kingdoms that is
Monera, Protista, Fungi, Animalia, and Plantae. The prokaryotic algae are
placed in the Monera and the eukaryotic algae in the Protista. Hence, the
algae do not belong to the kingdom of Plantae. However , it is widely
accepted that photosynthesis is a mutual characteristic. The perception
is that algae are ‘lower plants’ in distinction to the vascular ‘higher
plants.’

4. • Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll and other
pigments for carrying out photosynthesis. Algae can be multicellular or unicellular.
• Unicellular algae occur most frequently in water, especially in plankton. Phytoplankton is the
population of free‐floating microorganisms composed primarily of unicellular algae. In addition, algae
may occur in moist soil or on the surface of moist rocks and wood. Algae live with fungi in lichens.
• According to the Whittaker scheme, algae are classified in seven divisions, of which five are
considered to be in the Protista kingdom and two in the Plantae kingdom. The cell of an alga has
eukaryotic properties, and some species have flagella with the “9‐plus‐2” pattern of microtubules. A
nucleus is present, and multiple chromosomes are observed in mitosis. The chlorophyll and other
pigments occur in chloroplasts, which contain membranes known as thylakoids.
• Most algae are photoautotrophic and carry on photosynthesis. Some forms, however,
are chemoheterotrophic and obtain energy from chemical reactions and nutrients from preformed
organic matter. Most species are saprobes, and some are parasites.
GENERAL CHARACTERISTICS

5. • Reproduction in algae occurs in both asexual and sexual forms. Asexual reproduction occurs
through the fragmentation of colonial and filamentous algae or by spore formation (as in fungi).
Spore formation takes place by mitosis. Binary fission also takes place (as in bacteria).
• During sexual reproduction, algae form differentiated sex cells that fuse to produce a
diploid zygote with two sets of chromosomes. The zygote develops into a sexual spore, which
germinates when conditions are favorable to reproduce and reform the haploid organism having a
single set of chromosomes. This pattern of reproduction is called alternation of generations.

6. There are seven types of algae based on the different types of pigmentation
and the food reserves.
CLASSIFICATION
1. Green Algae (Chlorophyta)
2. Euglenophyta (Euglenoids)
3. Golden-Brown Algae And Diatoms (Chrysophyta)
4. Fire Algae (Pyrrophyta)
5. Red Algae (Rhodophyta)
6. Yellow-Green Algae (Xanthophyta)
7. Brown Algae (Phaeophyta)

8. 1. Green Algae (Chlorophyta)
Green algae are mainly found in aquatic habitats especially freshwater environments. Others can also
be found in salt water environments such as the ocean. They contain flagella which enables them to feed on
organic matter in their surroundings. Since green algae contain chloroplasts, they can process their own
food. They occur as unicellular or multicellular species containing thousands of cells. Examples include
horsehair algae and sea lettuce.
2. Euglenophyta (Euglenoids)
This type of algae contain chloroplasts and can synthesize their own food through the process of
photosynthesis. Euglena can be found in fresh and saltwater environments. Unlike other types of algae,
they do not have a cell-wall but instead, have a pellicle which is a protein-rich layer. They source their food
in their habitats, mainly feeding on unicellular organisms and carbon-rich foods.
3. Golden-Brown Algae And Diatoms (Chrysophyta)
The golden-brown algae and diatoms are the most widespread unicellular species of algae. There are about
100,000 species of Chrysophyta found in both fresh and saltwater habitats. Of the two types of
Chrysophta, diatoms are the most abundant type and occur in the ocean as the different types of planktons.
Golden-brown algae have small cells of only 50 micrometers. In the ocean, they occur as nanoplanktons
and normally have a rapid rate of productivity compared to the diato

9. 4. Fire Algae (Pyrrophyta)
Fire algae are unicellular organisms found in salt water environments with some few species found in
freshwater environments. They use flagella, for movement in the water. They consist of two different
types, namely; cryptomonads and dinoflagellates. Some species of fire algae are bioluminescent and light
the ocean at night. They produce neurotoxin which is harmful to humans and other organisms.
5. Red Algae (Rhodophyta)
Red algae are eukaryotic cells that do not contain flagella and centrioles and are mainly found in
oceans in the tropical regions. They thrive on solid surfaces such as reefs and may also be found
attached to other algae. Rhodophyta contains a cell wall that is made up of cellulose and other types of
carbohydrates. Some seaweeds are red algae.

10. 6. Yellow-Green Algae (Xanthophyta)
These unicellular organisms are the rarest and least prolific species of algae with only 450 to 650
species. Their cell walls are made of silica and cellulose with only a maximum of two flagella for
movement. They appear a lighter green since their chloroplasts lack a certain pigmentation. Yellow-green
algae are common in freshwater environments with some few species living in salt water environments.
7. Brown Algae (Paeophyta)
These are among the largest and most complex species of algae. They inhabit marine
environments. They contain photosynthesis organs and differentiated tissues. Brown algae have a life
cycle which involves the alternation of generations. Main examples of brown algae include giant kelp,
rockweed and sargassum weed. Some species can be large enough to be 100 meters in length.

11. REPRODUCTION
The algae reproduce by three different methods namely,
Vegetative Reproduction
Asexual Reproduction and
Sexual Reproduction.

12. Vegetative Reproduction in Algae:
Any vegetative part of the thallus grows into a fresh new organism in this form. This
does not entail the development of spores or the alternation of generations. This is the
most typical method for algae to reproduce.
The modes of vegetative reproduction in algae are as follows:
1. Budding:
Bud-like structures are defined in Protosiphon as a result of the proliferation of
vesicles that are separated from the parental body by a septum and develop into a
fresh new plant following detachment.
2. Cell Division or Fission:
It is the most basic type of reproduction. Synechococcus, Chlamydomonas, diatoms,
and other unicellular algae generally reproduce through this simple mechanism, known
as binary fission. The vegetative cell undergoes mitotic division and results in two
daughter cells, which then function as new individuals in this process.
3. Fragmentation:
The multicellular filamentous thallus is broken into many-celled fragments in this
process, all of which produces a new organism. Fragmentation in algae may occur by
chance, as a result of the formation of separation discs, or as a result of another
mechanical force or injury. Spirogyra, Zygnema, Oedogonium, Ulothrix,
Cylindrospermum, and other plants contain it.

13. Asexual Reproduction in Algae:
The creation of some types of spores — whether naked or freshly walled spores — is
needed for asexual reproduction. It is a mechanism of protoplast rejuvenation that
does not involve sexual fusion. Every single spore develops into a plant. There
occurs no alternation of generations in this process.
Asexual reproduction in algae can come in a variety of forms:
1. Akinetes:
Some filamentous algae's vegetative cells grow into akinetes, which are lengthened
thick-walled spore-like formations with ample food reserves (for example.,
Gloeotrichia). They have the ability to weather the storm. They germinate into new
individuals as ideal conditions arise.
2.Aplanospores:
Aplanospores are spores that are not mobile. Under unfavourable conditions, such
as drought, such spores can develop singly or their protoplast can split to form
several aplanospores within the sporangium (e.g., Ulothrix, Microspora). Some
algae in semi-aquatic habitats may also produce aplanospores.
3.Endospores:
These are tiny spores produced by the mother protoplast's divisions. Conidia and
gonidia are other names for them. After the breakdown of mother wail, they were
set free. The spores germinate immediately and grow into a new plant, such as
Dermocarpa, without having to rest.
4. Exospores:

14. Sexual Reproduction in Algae:
Except for individuals of the Cyanophyceae class, almost all algae undergo sexual
reproduction. Gametes unite to produce zygotes while sexual reproduction. The combination
of gametes from different parents will result in a new genetic establishment.
Sexual reproduction in algae are divided into five groups based on the structure,
physiological activity, and complexity of sex organs:
1.Autogamy:
Fusing gametes are formed from the very same mother cell throughout this process, and
then after fusion, these produce a zygote. For the reasons mentioned above,
autogamous plants do not display the emergence of any new characteristics, such as
Diatoms (Amphora normani).
2.Hologamy:
Vegetative cells of various strains (+ and -) act as gametes in certain unicellular
members, and then after fusion, they result in the formation of a zygote. This seems
to be an inefficient method in terms of multiplication, however, it does result in
the creation of new genetic varieties, such as Chlamydomonas.
3.Isogamy:
It is the merger of two gametes that are physiologically and morphologically
identical, resulting in the formation of a zygote. Isogametes are a form of gamete.
These are typically flagellates, such as Chlamydomonas Eugametos, Ulothrix, and

15. 4.Anisogamy:
The uniting gametes are physiologically and morphologically distinct during this
phase. The microgamete (male) is small and more aggressive, while the macrogamete
(female) is bigger and less active, such as Chlamydomonas braunii. Physiological
anisogamy differs from traditional anisogamy in that the uniting gametes share
morphological similarities but vary physiologically. Zygnema, Spirogyra, can be
some examples.
5.Oogamy:
It is a complex process in which a small motile (non-motile in Rhodophyceae) male
gamete (sperm or antherozoids) is fertilised by a large non-motile female gamete
(egg or ovum). Male gametes grow in antheridium, while female gametes grow in
oogonium, such as Polysiphonia, Oedogonium, Chara, Batrachospermum, Vaucheria,
Sargassum, Laminaria, and so on.

16. Thallus, plant body of algae, fungi, and other lower organisms formerly assigned to
the obsolete group Thallophyta. A thallus is composed of filaments or plates of cells and
ranges in size from a unicellular structure to a complex treelike form. It has a simple
structure that lacks specialized tissues typical of higher plants, such as a stem, leaves,
and conducting tissue.
THALLUS AND ITS
STRUCTURE
The algae exhibit a great diversity in the
organization of the plant body.
The plant body shows no differentiation
into true root, stem and leaves is called a thallus.
This term is used event if the plant is a unicell.

19. I. UnicelluarThallus:
The simplest form of the thallus is a unicell. These unicellular forms may be
motile or non-motile.
i) Motile Unicellular Thallus:
These unicellular structures possess flagella for locomotion.
They may be spherical, oval or pear shaped. It is considered to be most primitive type of thallus.
Chlorophyceae, Euglenophyceae, Chrysophyceae, Xanthophyceae Cryptophyceae are classes where this
thallus is common. Ex. Clamydomonas.
ii) Non-motile UnicelluarThallus:
These unicellular structures lack any kind of motility structures.
Ex. Chlorella, Chlorococcales, Desmids etc.

20. iii) Rhizodal Unicellular Thallus:
In this types no locomotive structures are present but the cells move with
the help of cytoplasmic outgrowth or rhizopodia. Xanthophyceae,
Chrysophyceae, Dinophyceae
are the classes in which this thallus is present. Ex. Chrysamoeba,
Rhizolekane.
II. MulticelluarThallus:
In this type more than one cell is present. It is again divided into
• Non-filamentous
• Filamentous

21. I) Non-filamentous Thallus:
In this following types are present-
A) Colonial Thallus:
These type of thallus consists of loose assemblage of indefinite cells mechanically held together in a common
gelatinous envelope.
It is known as colony. The cells in the colony have little or no dependence upon one another.
Motile colonial thallus:
it consists of motile, unicellular Chlamydomonas like cells held together in a common mucilaginous sheath. The
cell act together and bring about movement of the entire colony. Ex. Volvox.
Non-Motile Colonial Thallus:
In this type of thallus, indefinite number of small, non-motile cells are held together to form non-motile colonies.
They are free floating colonies Ex.-Pediastrum, Hydrodictyon.

22. B) Coenobial Colonies:
These types of thallus consists of definite number of cells enveloped in a mucilaginous sheath and arranged in a
particular manner. The cells of a coenobium are independent of each other. It may be motile or non-motile.
Motile CoenobialThallus:
The definite number of motile cells are embedded in a mucilaginous.
Ex,- Gonium ( 4 to 32 cells), Eudorina ( 4 to 12 cells).
Non-Motile CoenobialThallus:
Palmelloid colonies:
In this type of thallus, the vegetative cells are non-motile and are embedded in a mucilaginous matrix of irregular
shape and size.
The cells becomes motile during reproduction. The matrix is formed from the walls of individual cells. Ex.
Tetraspora, Palmella, Stichogloea.
Dendroid colonies:
In this type of thallus, the cells are united in a branching manner by localized production of mucilage at the base of
each cell. The whole colony looks like a tree in habit.
Ex.-Ecballocytes, Chrysodendron, Dindrobryon.
Rhizoidal Colonies:
The cells are united through rhizopodia Ex.-Chrysidiastrum, hrysorach

23. Multicellular FilamenotusThallus:
In this type of thallus, the cells are arranged in linear rows called the threads or filaments. The filament is the result of
repeated cell division of a non-motile cell in a single plane. The daughter cells in the chain remain united and further
keep on dividing in the same plane forming a filament.
i) Unbranched Simple Filaments:
In this type, the cells are arranged from end to end in a single file and held together firmly. It is long, thread like,
unbranchedtpe of multicellular thallus. The cells of the filament are alike,self-sufficient and independent of one
another.
Ex.- Spirogyra, Ulothrix, Eudogonium.

24. ii) Branched Filaments:
This type of thallus is formed when an occasional cell in the filament divide in second plane. The branches thus
arise as lateral outgrowths from the main filament. Ex.-Cladophora, Bulbochaete.
The filamentous forms evolved in two directions resulting in Pseudoparenchymatous and Parenchymatousfomrs.
The Pseudothallis may be fromed by juxtaposition of the branch system of a single axial thread or many axial
filaments.
If branches from a single filament are evolved as in Batrachospermum, the thallus is called uniaxial. If branches
of many axial filament aggregate ,the thallus is mlti axial, Eg. Nemalion.
The foliaceousparenchymantousthalli (Eg.Ulva) are of a very large size in brown sea weeds (Pheaophyceae). The
thallus is differentiated into central medulla, middle cortex and outer meristoderm.
Ex.-Laminaria, Microcystis.

25. Heterotrichousthallus:
It is the most advanced and evolved type of thallus. It consists of two parts – the basal portion of the thallus that
creeps along the substratum and is called prostrate system and upright filaments constituting the erect system.
In Stigeoclonium, both the erect and prostrate systems are equally developed.
The heterotrichousthallus has undergone modification by reduction or elimination of one or other of the systems. The
disappearance of erect system has resulted in the discoid form of thallis of Coleocheate.
Drapanaldia and Draparnaldiopsis are examples in which there is complete disappearance of the prostrate system and
a corresponding elaborate development of the erect system.

26. Siphanceous or Coenocytic thallus:
In this type the unicelluarethallus is enlarged to form a non-septate, multinucleate (coneocytic) sac-like or tubular
structures.Ex.-Characium and Acetabularia.
Characium is tubular and Acetabularia is umbrella-shaped. In Caulerpa the thallus is more elaborate and mimics
the
creeping shoots of aerial plants resembling a large moss or a fern. It is differentiated into a creeping structure
resembling a rhizome. The rhizome gives rise to holdfast from the under face and erect leaf shoots from its upper
face.

27. 1. Many algae are self feeders.
2. They contain photosynthetic pigment that help in the autotrophic nutrition.
3. They follow photo-autotrophic mode of nutrition as they make their own
food using the sunlight and other photosynthetic apparatus.
4. Some algae utilize organic nitrogen or carbon sources and nutrients in soil
or water to synthesize essential oils, fats and proteins via a heterotrophic
mode of nutrition.
5. A few Algae species show the mixotrophic mode of nutrition, in which they
utilize both organic and inorganic sources to fulfil their growth and
nutritional needs.
6. Mode of nutrition in algae - Autotrophic
MODE OF NUTRITION

28. DISTRIBUTION
• Algae are present everywhere in distribution.
• They occur in great abundance in oceans, seas, ponds, fresh water, steams and Salt Lake.
• Many are found in soil of dam, rocks, stones, and bark of tree and on other animals and plants surface.
• Small aquatic forms make a large of the free floating microscopic life in water, called plankton.
• Phytoplankton is made up of plants i.e. algal forms.
• Zooplankton is composed of animal organisms.
• Some Species of algae grow on the snow and ice of polar region and mountain peaks.
• Some, algae grow in hot springes at temperature has high as 55°C.
• Some are Endophytice. They are not free living but live in other organisms such algae are widespread
in protozoa, molluscus, sponges and corals.

29. BENEFITS OF ALGAE