Download Bio I Lab Instructor: Dr. Rana Tayyar Lab X Kingdoms Bacteria

Bio I Lab
Instructor: Dr. Rana Tayyar
Lab X
Kingdoms Bacteria, Archaea, Protista, and Fungi
Taxonomy is the identification and classification of species. The taxonomy developed by Linnaeus (eighteenth
century) had two main features:
First: the development of the binomial nomenclature system, which assigned to each species a two-part Latin name.
This is also referred to as the “scientific name”. The first word is the genus to which the species belongs. It is
always written in italics or underlined. Example: Homo sapiens or Homo sapiens for humans.
Second: the adoption of a filing system for grouping species into a hierarchy of increasingly general categories.
The following is a list of the main divisions in classification (an example of human classification is shown):
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Homidae
Genus: Homo
Species: sapiens
A domain is the top level grouping. Three domains are recognized: Archaea, Eubacteria and Eukaryota.
There are six kingdoms: Bacteria, Archaea, Protista, Fungi, Plantae and Animalia. The last four kingdoms belong to
the Eukaryota domain.
Four kingdoms will be covered in today’s lab: Bacteria, Archaea , Protista and Fungi.
Bacteria and Archaea:
Until recently, Archaea and Bacteria belonged to one kingdom, Monera. Bacteria and Archaea are both
prokaryotes. They are mainly unicellular. Remember that prokaryotic cells have no membrane-bound organelles.
Instead of a nucleus, they have a nucleoid with circular DNA. They do possess ribosomes for protein synthesis.
They have a cell membrane as well as a cell wall. Prokaryotes reproduce mainly asexually (binary fission).
Archaea are mainly anaerobic bacteria that live in extreme environments:
Extreme salt → Halophiles
Extreme temperatures → Thermophiles
Archaea do not have peptidoglycan in their cell wall. Peptidoglycan consists of polymers of modified sugars crosslinked by short polypeptides.
Bacteria can be both aerobic and anaerobic. Unlike members of Archaea, bacteria have peptidoglycan in their cell
wall. They often have symbiotic relationships with animals and plants. Some parasitic species are pathogenic
causing disease in the host by invading its tissues or poisoning it with endotoxins or exotoxins.
Endotoxins are components of the outer membranes of certain bacteria such as the Salmonella sp.
Exotoxins are proteins secreted by some bacteria (such as E.coli) and are responsible for producing disease
symptoms even without the prokaryote being present.
Antibiotics are used to treat different kinds of bacterial infections. They have different modes of action. Some
antibiotics inhibit the reproduction of bacteria by interfering with the formation of the peptidoglycan cell wall.
Others attack the ribosomes. However, increased and irresponsible use of antibiotics leads to antibiotic resistance.
The increased prevalence of antibiotic resistance is the outcome of evolution: survival of the fittest. What does that
mean? In any population of organisms, there are some natural variants. In the case of bacteria, these variants might
have traits that withstand antibiotic attack. When a person takes an antibiotic, the drug will kill the defenseless
bacteria leaving behind the ones that resist it. These bacteria will reproduce at a very fast rate making the resistant
bacteria the predominant form.
For example, we do not need to use antibacterial soap. It kills the beneficial bacteria and could lead to the
development of resistant strains of harmful bacteria.
Using Gram staining (Gram staining is based on the ability of bacteria cell wall to retaining the crystal violet dye
during solvent treatment), bacteria with thick layer of peptidoglycan stain purple and are referred to as gram-positive
bacteria. Bacteria with thin layer of peptidoglycan will stain pink and are known as gram-negative bacteria
(Salmonella sp.). They are generally more pathogenic than the gram-positive bacteria.
Most prokaryotes are heterotrophs, meaning they obtain their carbon atoms from organic compounds. However,
some prokaryotes are autotrophs, making their own organic compounds from inorganic sources.
Three main bacterial shapes are recognized:
Sphere: Coccus
Rod: Bacillus
Spiral: Spirillum
Endospore: A thick-coated resistant cell produced within a bacterial cell exposed to harsh environment (specialized
resting cell). A temperature of 120oC is needed to kill endospores.
Activities:
►You will be looking at the prepared slides of the following bacteria types:
Gram positive
Gram negative
Coccus
Bacillus
Spirillum
Cyanobacteria
►Antibacterial properties of household items.
Protista:
The kingdom Protista is the most diverse kingdom. Members do not have a lot in common. However, all protists
are eukaryotes. Most species of protists are unicellular. Colonial and multicellular species are also found. Both
types of reproduction (sexual and asexual) take place in protists.
Metabolically, protists could be:
Photoautotrophs: these are self-feeders that use light energy to drive the synthesis of organic compounds from CO 2.
Heterotrophs: creatures that feed by ingesting food particles.
Mixotrophs: organisms that combine photosynthesis and heterotrophic nutrition.
In today’s lab, we will cover:
Animal-like protists (ingestive): These are eukaryotic heterotrophs. You will be looking at:
►Amoeba (both preserved and prepared slides): main features include pseudopods and contractile vacuole.
►Paramecium (both prepared and live samples): notice the cilia, contractile vacuoles at both ends of the cell, the
macronucleus and micronucleus.
►Trypanosomes (prepared slide): move by flagellum and are characterized by the presence of kinetoplast
(mitochondrial DNA).
►Trichonympha: has a flagellum and lives in the gut of termites.
Plant-like protists (photosynthetic): These are autotrophic photosynthetic creatures. You will be looking at
prepared slides of:
►Euglena: characterized by spindle-shaped body, moves by flagellum and has a red eye spot near the base of the
flagellum (serves as light shield). It is a mixotroph.
►Dinoflagellates: these unicellular eukaryotes are characterized by a pair of flagella in perpendicular grooves.
Beating of the flagella causes the cell to spin as it swims. Dinoflagellates blooms (episodes of explosive population
growth) cause red tides in coastal water due to the predominant red pigments (xanthophylls) in their chloroplasts.
Some species release neurotoxins that are deadly to invertebrates and fish.
►Diatoms: characterized by unique glass-like wall containing silica. The pigment fucoxanthin gives the diatoms
their yellowish-brownish appearance. They store their food in the form of oil rather than carbohydrate.
►Green algae:
Volvox, (fresh specimen): colonial protist. Daughter colonies live inside the parent colony until they burst free.
Cells within a colony are usually connected by strands of cytoplasm; if isolated, these cells cannot reproduce.
Fungus-like protists (absorptive): These creatures used to be classified as fungi. They absorb nutrients from their
surroundings (heterotrphs).
Your lab manual gives a good description of the creatures you looked at. Make sure you can identify them under the
microscope, you can describe the way they move, their habitat and you can classify them as autotrophs or
heterotrophs.
Fungi:
Fungi are eukaryotes. They are heterotrophs that acquire their nutrients by absorption. Fungi can be decomposers,
parasites or mutualistic symbionts.
Most fungi are multicellular (except for yeasts that are unicellular). Fungi are constructed of hyphae, which are
minute threads composed of tubular walls surrounding plasma membranes and cytoplasm. Hyphae form an
interwoven mat called a mycelium. Generally, hyphae are divided into cells by cross-walls called septa. Pores in
the septa allow ribosomes, mitochondria and even nuclei to flow from one cell to another. In some cases, hyphae
are nonseptate with continuous cytoplasm and several nuclei. Cell walls of fungi are made up of chitin, a strong but
flexible nitrogen containing polysaccharide. Hyphae can be aggregated into reproductive structures called a fruiting
body. Fungi have sexual and asexual reproduction. The former results in genetically diverse spores whereas the
latter generates genetically identical spores.
Most fungi have three distinct phases in their life cycles. They have diploid and haploid phases. They also have a
unique third phase called dikaryotic phase, in which cells contain two haploid nuclei (n + n). During sexual cycles,
syngamy (fusion of hyphae of compatible mating types) occurs in two stages that are separated in time (they do not
occur simultaneously). Plasmogamy is the fusion of cytoplasm whereas karyogamy is the fusion of nuclei. After
plasmogamy, the nuclei from the two parents pair but do not fuse forming a dikaryon. When karyogamy takes
place, the diploid cell (2n) undergoes immediate meiosis that results in haploid spores.
The Kingdom Fungi is divided into four phyla which are classified on the basis of spore types or reproductive
structures they have:
Chytridiomycota: Chytrids are microscopic fungi found everywhere from ponds, puddles, soil, mud, etc. They are
mainly decomposers. Some are parasitic (Batrachochytrium sp., affecting frogs worldwide). They are the only
fungi with flagellated spores (zoospores). The flagellum propels the spores toward light and food.
Zygomycota (the zygote fungi): The name is derived from the type of the reproductive structure they produce, the
zygosporangium. Zygosporangium is a resistant structure formed during sexual reproduction. It is the result of the
fusion of two haploid hyphae of different mating types. Bread mold (Rhizopus sp.) belongs to this phylum.
Ascomycota (the sac fungi): Members of this phylum produce spores into saclike structures called asci (single,
ascus). The two different mating types in this phylum are referred to as ascogonium (acts as female) and
antheridium (acts as male). These fungi are diverse. Some members are decomposers of paint to jet fuel. Others
are highly valued delicacies such as morels and truffles. Yeast which is used for baking breads and brewing beer
belongs to this phylum.
Basidiomycota (the club fungi): These fungi have spore bearing structures called basidia (single, basidium).
Mushrooms are members of this phylum. Basidia grow along strips of tissues called gills on the underside of the
mushroom cap.
You will be exploring these four phyla in the lab. Be prepared to make your own index card about each
phylum/sample you will be observing. Include the main characteristics of each phylum and the life cycle of the
fungus representing that phylum. You should be able to identify all the samples you see in the lab and the structures
you see under the microscope.
Fungi as symbionts:
Lichen: A lichen is a symbiotic association of millions of photosynthetic microorganisms (such as cyanobacteria
and algae) held in a mesh of fungal hyphae. The algae/cyanobacteria provide the fungus with food and the fungus
usually gives the lichen its overall shape and structure.
Mycorrhizae: These are mutualistic associations of plant roots and fungi. Over 95% of vascular plants have
mycorrhizae. The mycorrhizae enhance the absorption of minerals by the roots. The fungus obtains carbohydrates
from the photosynthetic plants.