Introduction to microbiology

1. M I C R O B I O L O G Y
a n i n t r o d u c t i o n
ninth edition TORTORA  FUNKE  CASE
Instructor :Sir Muzzamil

2.  Microbiology is the study of microorganisms.
 The overall theme of the Microbiology course is to study the relationship
between microbes and our lives.
 Microorganisms (microbes) are organisms that are too small to be seen
with the unaided eye, and usually require a microscope to be seen.
 This relationship involves harmful effects such as diseases and food
spoilage as well as many beneficial effects.
 “Germ” refers to a rapidly growing cell.
 Microorganisms include:
1. Bacteria
2. Fungi (yeasts and molds)
3. Microscopic Algae
4. Protozoa
5. Viruses, Viroids, Prions.
Microbes in Our Lives

3.  These small organisms are usually associated with major diseases such as
AIDS, uncomfortable infections, or food spoilage.
 However, the majority of microorganisms make crucial contributions to the
to the welfare of the world’s inhabitants by maintaining balance of living
organisms and chemicals in our environment.
 Therefore, Microorganisms are essential for life on earth.
1. Photosynthesis: Marine and freshwater MO (Algae and some bacteria)
capture energy from sunlight and convert it to food, forming the basis
of the food chain in oceans, lakes, and rivers and generates oxygen
which is critical for life on Earth.
Microbes in Our Lives

4. 2. Decomposers: Soil microbes break down dead and decaying matter and
recycle chemical elements that can be used by other organisms.
3. Nitrogen Fixation: Some bacteria can take nitrogen from air and
incorporate it into organic compounds in soil, water, and air.

5. 4. Digestion: Human and many other animals have microorganisms in their
digestive tract, that are essential for digestion and vitamin synthesis.
a. Cellulose digestion by ruminants (cows, rabbits, etc.)
b. Synthesis of Vitamin K (for blood clotting) and Vitamin B (for
metabolism) in humans.
5. Synthesis of chemical products: MOs have many commercial applications,
such as the synthesis of acetone, organic acids, enzymes, alcohols.
6. Medicine: Many antibiotics and other drugs are naturally synthesized by
microbes.
 Penicillin is made by a mold.
7. Food industry: many important foods and beverages are made with microbes:
vinegar, pickles, alcoholic beverages, green olives, soy sauce, buttermilk,
cheese, yogurt, and bread.
Microbes in Our Lives

6. 8. Genetic engineering: recombinant microbes produce important
a. Medical and therapeutic products: human growth hormone, insuline,
blood clotting factor, recombinant vaccines, monoclonal antibodies,…etc.
b. Commercial products: cellulose, digestive aids, and drain cleaner.
9. Medical Research: Microbes are well suited for biological and medical
research.
 Though only a minority of MOs are pathogenic (disease-producing), practical
knowledge of microbes is necessary for medicine and related heath sciences.
Microbes in Our Lives

7. How are Microbes Used in Medicine and Research
 Microbes are used to deliver “new” genes in gene
therapy.
 Microbes are used to clone genes so we can study and
identify them
 Microbes are used to commercially make proteins such
as insulin or human growth hormone

8.  INSECT BEST CONTROL BY MOs
 Insect pest control is important for both agriculture and the prevention
of human diseases.
 Bacillus thuringiensis infections are fatal for many insects but harmless
to other animals, including humans, and to plants.
 The bacteria produce protein crystals that are toxic to the digestive
systems of the insects.
 The toxin gene has been inserted into some plants to make them insect
resistant.
Microbes and Human Welfare

9. Microbes and Human Disease
NORMAL MICROBIOTA
 We all live in a world filled with microbes, and we all have a variety of
microorganisms on and in our bodies.
 Microbes normally present in and on the human body are called normal
microbiota, or flora.
 Bacteria were once classified as plants giving rise to use of the term
flora for microbes.
 This term has been replaced by microbiota.
 The normal microbiota not only harmless, but also benefit us.
1. Some protect us against disease by preventing the over-growth of
harmful microbes.
2. Others produce useful substances such as vitamine K and B.
 Unfortunately, under some circumstances normal microbiota can make us
sick or infect people we contact.

10.  Emerging infectious diseases (EID): are diseases that are new or changing and
are increasing or have the potential to increase in incidence in the near future.
 Some factors that have contributed to the emergence of EIDs:
a. Evolutionary changes in existing organisms.
b. The spread of known diseases to new geographic regions or populations by
modern transportation.
c. Increased human exposure to new, unusual infectious agents.
1. West Nile encephalitis
 Caused by West Nile virus
 First diagnosed in the West Nile region of Uganda in 1937
 Appeared in New York City in 1999
Microbes and Human Disease
EMERGING INFECTIOUS DISEASES

11. Emerging Infectious Diseases
3. Escherichia coli O57:H7
a. Toxin-producing strain of E. coli
b. First seen in 1982
c. Leading cause of diarrhea worldwide
4. Ebola hemorrhagic fever
a. Caused by Ebola virus
b. Causes fever, hemorrhaging, and blood clotting
c. First identified near Ebola River, Congo
d. Outbreaks every few years.
6. Avian influenza A (H5N1)
a. Caused by Influenza A virus (H5N1)
b. Primarily in waterfowl and poultry
c. Sustained human-to-human transmission has not occurred yet

12. Emerging Infectious Diseases
9.Acquired immunodeficiency syndrome (AIDS)
a. Caused by Human immunodeficiency virus (HIV)
b. First identified in 1981
c. Worldwide epidemic infecting 44 million people; 14,000 new infections daily
d. Sexually transmitted disease affecting males and females
e. In the United States, HIV/AIDS cases: 30% are female and 75% are
African American

14. Bacteria can make oxygen!

15. Bacteria can kill insects that eat crops!
Cotton
Vegetables/Fruits

16. Bacteria make us smarter!

17. Bacteria make medicine!

18. Bacteria help night vision!

19. Bacteria help plants grow!

20. What makes some bacteria harmful?

21. How do bacteria from the environment cause
you harm?
Bacteria enter your
body
Grow to huge
numbers
Disease

22. Examples of harmful bacteria
Streptococcus pyogenes- sore throat
Streptococcus pneumoniae-
ear infections and
pneumonia
Enterotoxigenic E.
coli- diarrhea from
food that has
harmful bacteria on
it
Staphylococcus aureus-
skin infections

23. How can I come in contact with
harmful bacteria?
Air Dirty objectsCuts and
scrapes
Some insects
Food that is
contaminated with
harmful bacteria
pneumonia
E. coli
Lyme disease
Stomach problems

24. Protect ourselves from
bad bacteria
What can we do???

25. When you’re at common places…

26. Food to eat…
Eat fully cooked meat
Un- or semi-cooked meat
may contain harmful
bacteria

27. Food to eat…
Eat fully washed vegetables
and fruits
Unwashed fruits or
vegetables may contain
harmful bacteria

28. If you were sick…
Go to see a doctor
This would avoid further
infecting your classmates and
your family members.

29. Protect ourselves from
bad bacteria
Things we can do:
1 Wash our hands whenever needed.
2 Cover your mouth when coughing or sneezing at
common places.
3 Eat fully cooked or thoroughly cleaned food.
4 Go to see a doctor if you were sick.

30. What if a Gene is Faulty
 Medical advances has proposed gene therapy as a
possible solution to “fixing” faulty genes.
 Microbes are often used as a delivery method for the
new gene.
 Virus can deliver DNA into cells that need a new gene.

31. Microbial Diversity and Habitats
 Microbes live in a variety of habitats because of their
abilities to
 Use a variety of carbon and energy sources
 Grow under different physical conditions
 Extremophiles live in extreme conditions
 pH
 Temperature
 Salinity

32. Symbiosis
 Two differing organisms living together in a close
association that is beneficial to one or both of them
 Examples of symbiosis between animals and microbes:
 Ruminants (such as sheep and cows) and the
bacteria in the rumen
 Mycorrhizae contribute to plant growth

33. Mycorrhizae
 Fungi living in close association with plant roots
 Extend surface area of roots

34. Figure 27.1 Mycorrhizae.
Endomycorrhiza (vesicular-
arbuscular mycorrhiza). A fully
developed arbuscule of an
endomycorrhiza in a plant cell.
(The term arbuscule means
“little bush.”) As the arbuscule
decomposes, it releases
nutrients for the plant.
Ectomycorrhiza. The mycelial mantle
of a typical ectomycorrhizal fungus
surrounding a Eucalyptus tree root.
Plant
cell wall
Arbuscule
Mycelial mantle

35. Figure 27.2 Mycorrhizae and their considerable commercial value.
Mycorrhizae infection influences
the growth of many plants. The pine
seedling on the left was inoculated
with mycorrhizae; the seedling on
the right was not.
Truffles. An ectomycorrhiza,
usually of oak trees.

36. Biogeochemical Cycles
 Recycling (oxidation and reduction) of chemical
elements.
 Typical soil has millions of bacteria in each gram.

37. Carbon Cycle

38. The primary biogeochemical cycle is the carbon cycle.
All organisms, including plan ts, microbes, and animals, contain
large amounts of carbon in the form of organic compounds such
as cellulose, starches, fats, and proteins.
When you look at a tree, you might think that its mass is from the
soil where it grows. In fact, its great mass of cellulose is derived
from the 0.03% of carbon dioxide in the atmosphere.
the first step of the carbon cycle in which photoautotrophs such
as cyanobacteria, green plants, algae, and green and purple
sulfur bacteria fix (incorporate) carbon dioxide into organic
matter using energy from sunlight.

39. Next step of the cycle, chemoheterotrophs such as animals
and protozoa cat autotrophs and may in turn be eaten by
other animals.
Thus, as the organic compounds of the autotrophs arc
digested and resynthesized, the carbon atoms of carbon
dioxide are transferred from organism to organism up the
food chain.
Chemoheterotrophs, including animals, use some of the
organic molecules to satisfy their energy requirements.

40. When this energy is released through respiration, carbon dioxide
immediately becomes available to start the cycle over again.
When plants and animals die, these organic compounds are
decomposed by bacteria and fungi.
During decomposition, the organ ic compounds are oxidized, and
COl is returned to the cycle.
Carbon is stored in rocks, such as limestone (CaC03), and is
dissolved as carbonate ions (CO/-) in oceans.

41. Figure 27.3 The carbon cycle.
CO2 in atmosphere
Burning
Wood and
fossil fuels
Plant
respiration
Animal
respiration
Plants, algae,
cyanobacteria
Photosynthetic
fixation
KEY
Fixation
Respiration
Plants Animals
CH4 +CO2
Dissolved
CO2Decomposition
Dead
organisms
Soil and
water microbes
Fossil
fuels
Aquatic
bacteria
Plants, algae,
cyanobacteria
Photosynthetic
fixation
Dead or ag nisms,including aquatic animals

42. Nitrogen Cycle

43. All organisms need nitrogen to synthesize protein, nucleic acids, and
other nitrogen -
containing compounds.
Molecular nitrogen (N2) makes up almost 80% of the Earth's
atmosphere.

44. N2
Nitrogen fixation
Ammonia (NH3)
Nitrate ion (NO3
–
)
Pseudomonas
N2
Nitrite ion (NO2
–
)
Nitrobacter
Nitrate ion (NO3
–
)
Ammonium ion (NH4
+
)
Nitrosomonas
Nitrite ion (NO2
–
)
Amino acids (–NH2)
Microbial ammonification
Ammonia (NH3)
Proteins and waste products
Microbial decomposition
Amino acids
The Nitrogen Cycle

45. Figure 27.4 The nitrogen cycle.
KEY
Ammonification
Fixation
Nitrification
Denitrification
(N2)
(N2O)
Nitrites
(NO2
–
)
Nitrates
(NO3
–
)
Nitrites
(NO2
–
)
Ammonia
(NH3)
Free nitrogen gas
(N2) in atmosphere
Leguminous
plants
Nitrosomonas
Nitrobacter
Denitrifying bacteria
(Pseudomonas,
Bacillus licheniformis,
Paracoccus
denitrificans,
and others)
Decay organisms
(aerobic and
anaerobic bacteria
and fungi)
Symbiotic
Rhizobium,
Bradyrhizobium
Nonsymbiotic
Azotobacter,
Beijerinckia,
cyanobacteria,
Clostridium
Industrial
fixation as
fertilizer
Fixation
Protein
from
dead cells
Decomposition
Assimilation
Ammonification
Nitrification
Denitrification

46. Nitrogen Fixation
 In root nodules
 Rhizobium
 Bradyrhizobium
 Frankia
 In rhizosphere
 Azotobacter
 Beijerinckia
 Clostridium pasteurianum
 Cyanobacteria: heterocysts

47. An infection thread is
formed, through which
bacteria enter root cells.
Enlarged root cells
form a nodule.
Bacteria change into
bacteroids; packed
root cells enlarge.
Rhizobia attach
to root hair.
Pea plant
Root
hairs
Rhizobia
Infection
thread
Bacteroids
Root
Nodules
Figure 27.5 The formation of a root nodule.

48. Sulfur Cycle

49. o The sulfur cycle and nitrogen cycle resemble each other in the
sense that they represent numerous oxidation states of these
elements.
o Elemental sulfur is released from decaying microbes.
o Elemental sulfur is essentially insoluble in temperate waters,
and microbes have difficulty absorbing it.
o Beggiatoa, they can further oxidize the sulfur to sulfate ions.

50. oHydrogen sulfide can be used as an energy source by Thiobacillus
to produce sulfate ions and sulfuric acid.
oTiliobacillrlS can grow well at a pH as low as 2 and has practical
uses in mining.

51. Figure 27.7 The sulfur cycle.
SH sulfhydryl
groups of proteins
SO2 H2SO3 H2S
SO4
2–
S0
H2S
S0
Burning of
fossil
fuels
Solution,
plant
uptake
Plant
decay
Excretion
Elemental
sulfur
Volatile
sulfur
emissions
KEY
Dissimilation
Assimilation
Oxidation
Anaerobic
respiration
Reduction by
Desulfovibrio Microbial
oxidation
Purple
and green
bacteria
Decomposition
by microbes
(dissimilation)
Assimilation by plants
and bacteria
Thiobacillus

52. Proteins and waste products Amino acids
Microbial decomposition
Amino acids (–SH)
Microbial dissimilation
H2S
H2S
Thiobacillus
SO4
2–
(for energy)
SO4
2–
Microbial and plant assimilation
Amino acids
The Sulfur Cycle

53. Thank you