Second Quarter Grade 7

1. Science 7
Lesson 4
Microorganisms

2. Microorganisms
Lesson 4

3. Microorganisms
● Living things may be multicellular or
unicellular.
● Unicellular or one-celled organisms are
mostly invisible to the naked eye.
● Microorganisms- organisms that can be
seen through microscope.

4. Microorganisms
Microorganisms
- micros = small
- Organismos = organisms
Microbiology
- A field in biology that deals with the study of
microorganisms.

5. Microorganisms
Anton Van Leeuwenhoek
- Discovered animalcules in a drop of
rainwater using microscope which he
designed.

6. Diverse
Can be
found
everywhere Can live on
land, in
water, and
in the air.

7. “Microbes can be found
everywhere because they are
highly adaptable to extreme
environmental conditions.”

8. Microorganisms
Pathogens
- Organisms that cause diseases.
● Some microorganisms are beneficial and are
needed by other living things.
● They also play a critical role in the nutrient
cycles in ecosystems.

9. Bacteria

10. Bacteria
● Bacteria are simple, unicellular
organisms.
● Bacteria obtain nutrients from their
environment.
● Some species are free-living
(saprotrophs), while others are
parasitic.

11. Bacteria
● As organisms invade the body of
the hosts, they excrete waste
materials and various types of
toxins so as to invade the hosts’
tissues.

12. Bacteria
Bacterial cells have the following
structural components:
● Cell envelope
● Cytoplasm
● Appendages

13. Bacteria
➢ Cell envelope
- Cell wall
- Capsule
- Plasma membrane

14. Bacteria
➢ Cytoplasm
- Chromosomes
- Ribosomes
- Some storage granules

15. Bacteria
➢ Appendages
- Flagella
- Pili or fimbriae

16. Distinct Groups of Bacteria
● Bacteria may be Gram positive or Gram
negative.
● Such distinction can be observed when
bacteria are subjected to a Gram-staining
process.
● Hans C.J. Gram, a microbiologist,
developed the Gram-stain technique.

18. Hans Christian
Joachim Gram
(13 September 1853 – 14
November 1938)

19. Distinct Groups of Bacteria
● Gram-positive bacteria are those that retain
the purple crystal violet stain when subjected
to the Gram-staining procedure.
● Gram-negative bacteria do not retain the
crystal violet stain, and thus, they are
counterstained by safranin, a dye that gives
them the reddish or pinkish color.

20. Distinct Groups of Bacteria
● This distinction is attributed to the
composition of the bacterial cell wall. In
bacteria, the cell wall is a very essential
structure for a very important reason-it is an
important receptor site for the attack of
antibiotics and other drugs (for pathogenic
bacteria).

22. Distinct Groups of Bacteria
● As compared to Gram-positive bacteria,
Gram- negative bacteria are more
resistant against antibodies.
● The existence of these two strains is the
basis used by physicians in prescribing
medicines to cure bacterial infections.

23. Bacterial Shapes and Cellular Arrangements
● Microbiologists employ a wide variety of techniques
as they classify bacteria.
● A bacterial colony is a group of the same kind of
bacteria growing together on a specific culture
medium placed on a petri dish.

24. Bacterial Shapes and Cellular Arrangements
● Various staining processes as well as analysis of the
DNA structure of the bacterial species are also used
in identifying them.

25. Bacterial Shapes and Cellular Arrangements
The most basic method that microbiologists used in
identifying bacteria is to view them under the microscope
to identify their:
1. Shapes;
2. the cell arrangement or groupings that they form; and
3. other features, like the number and arrangement of
the flagella.

26. In terms of shape, bacteria
fall into three morphological
categories:
1. Cocci
2. Bacilli
3. Spirilla

27. Cellular arrangement pertains
to how the bacterial cells are
arranged or grouped after
their cells divide, whether
singly, in chains, or in
clusters.

28. Cocci (Singular: coccus)
- are round bacterial cells.

29. ● Cocci can exist singly;
● as diplococci (in pairs);
● as packs like tetrads (consisting of four
cells);
● as sarcinae (consisting of eight cells);
● as streptococci (in chains); and
● as staphylococci (in clusters like a bunch
of grapes).

31. ● Bacilli (Singular: bacillus) are
rod-shaped or bacteria.
● The length of the cell varies
according to age and
environmental conditions.

32. ● Bacilli unlike the cocci bacteria have
fewer groupings since they only
divide across their short axis.
● Thus, only exist singly, as
diplobaccilli, and as streptobacilli.
● Escherichia coli and Bacillis
megaterium are respective examples
of single and streptobacilli.

34. ● Spirilla (Singular: spirillum) are curved
(vibrio), twisted or spiral-shaped
bacteria with fairly rigid bodies.
● Many species of spirilla are flagellated
and are capable of movement.
● A group of known as spirochetes have
helical bodies that are long, slender,
and flexible bacilli.

36. Reproduction in Bacteria
● One contributing factor why
bacteria can thrive in different
kinds of environment is
reproduction.
● Bacteria are reproductive experts.

37. Reproduction in Bacteria
Do you know that a single bacterium
can become two bacteria in a span of
20 minutes? Imagine the number of
bacteria that will be produced in a
span of 24 hours.

38. ● Bacteria reproduce both asexually and
sexually.
Three types of asexual reproduction
have bee identified among bacteria-
1. Binary fission
2. Budding
3. Spore-formation

42. ● The first two are considered the simplest
and the fastest methods of producing
more bacteria.
● The sexual method is considered a rare
phenomenon that can happen in some
special circumstances. The sexual
method is through genetic recombination
in different strains of bacteria.

43. ● Genetic recombination is the
exchange of genetic material
between different organisms which
leads to production of offspring with
combinations of traits
● These new traits will give them the
advantage for survival in the new
environment.

44. Economic Importance of Bacteria
● Humans consider bacteria as dangerous
organisms. This is because of the harmful
roles that bacteria play in causing diseases
and food spoilage.
● Bacteria are economically important as these
microorganisms are used by humans for
many purposes.

45. Economic Importance of Bacteria
● The beneficial uses of bacteria include the production
of traditional foods such as fudge, yogurt, cheese,
and vinegar. Microbes are also important in agriculture
for the compost and fertilizer production.

46. Harmful Effects of Bacteria
● Many species of bacteria cause 90% of
the known diseases that afflict humans.
Some can cause food spoilage and
deterioration of some household articles
and objects. It is also important that you
know some of them so that proper health
measures can be employed.

47. Harmful Effects of Bacteria
● Some types of bacteria can cause diseases
in humans, such as cholera, diptheria,
dysentery, bubonic plague, pneumonia,
tuberculosis (TB), typhoid, and many
more. If the human body is exposed to
bacteria that the body does not recognize as
helpful, the immune system will attack them.

48. Protists
● It affects humans and other organisms
because they are disease-causing.
● Some protists are beneficial as well.

49. Protozoans
Some species of protozoans or the "animal-like"
protists are disease causing or pathogenic.

50. Protozoans
a. Entamoeba histolytica
● a species of amoeba, is parasitic and can cause
amebic dysentery.
● The parasite lives in the intestine of humans and
feeds on intestinal walls causing bleeding ulcers.
● The disease can spread when the amoeba forms
resistant cysts that can pass out of the body
through the feces.

52. Protozoans
a. Entamoeba histolytica
● Drinking and eating contaminated water and
food can infect a person.
● Certain prescribed drugs can treat amebic
dysentery.
● It can be prevented by proper sewage disposal
and sterilization of contaminated utensils.

53. Protozoans
B. Trypanosoma gambiense
● It is the protozoan species that can cause sleeping
sickness.
● The parasite is spread to humans and other domestic
animals by the bite of an infected tsetse fly.
● The parasite multiplies in the blood releasing toxins.
● The symptoms of the disease include weakness,
sleepiness, and fever. If untreated, the victim usually
dies.

57. Protozoans
C. Trichonympha
● It is another flagellated protozoan that lives in
symbiosis in the digestive tract of termites.
● Termites are insects that feed on wood but they lack
the necessary enzymes to breakdown wood.
● Thus, the protozoan breaks down the wood eaten
by the termite and both organisms absorb and use
the nutrients.

59. Protozoans
D. Plasmodium
● It is the protozoan that causes the malarial fever in
humans. The malarial disease is spread by the bite
of a mosquito of the genus Anopheles.
● This protozoan exhibits a life cycle involving the
asexual spore-producing stage and the sexual
stage.
● Humans harbor the asexual stage and the spores
invade and multiply within the blood cells.

60. Protozoans
D. Plasmodium
● Consequently, the blood cells break
causing the characteristic chills and
fever in humans.
● The mosquito, which is the intermediate
host, harbors the sexual stage.

61. Protozoans
D. Plasmodium

62. Protozoans
Plant-like protists
● One microscopic algal group that impacts other organisms,
including humans, is the unicellular phytoplankton known as
the dinoflagellates.
● These protists reproduce by binary fission, and their
population can double in a limited span of time if the water is
polluted.

63. Protozoans
Plant-like protists
● Excessive increase in the population growth
of dinoflagellates is a phenomenon called
algal bloom, popularly known as red tide.
● Red tides produce toxins that kill much of the
coastal wildlife and can cause paralysis and
other illnesses or even death to humans.

66. Fungi
Some species of fungi play a key role in nature and are
economically important to humans.
1. The mycorrhiza is the genus that lives in symbiosis with
some vascular plants providing them with the essential
nutrients in exchange for some materials, which the
fungus cannot manufacture.
2. Fungi are decomposers. They break down dead
remains of organisms to continue the cycle of materials
in the ecosystem.

69. 3. Some species of mushroom (Agaricus) are edible and
are rich sources of proteins and other essential nutrients.
4. Some species are sources of drugs like aspergillic acid
(Aspergillus flavus) and antibiotics like penicillin.

70. Review
Lesson 4

71. I. Modified True or False.
1. Living things may be multicellular or
unicellular.
2. Unicellular organisms are mostly
visible to the naked eye.
3. Microorganisms are organisms that
can be seen through microscope.

72. 4. Robert Hooke discovered
animalcules in a drop of
rainwater.
5. Micros means big.
6. Pathogens are organisms that
cause diseases.

73. 7. Anton Van Leeuwenhoek developed
the Gram-stain technique.
8. Entamoeba histolytica is parasitic
and can cause amebic dysentery.
9. Gram-negative bacteria are those
that retain the purple crystal violet
stain.
10. Fungi are decomposers.

74. 11. A bacterial colony is a group of the same kind
of bacteria growing together on a specific culture
medium placed on a petri dish.
12. Black tides produce toxins that kill much of
the coastal wildlife.
13. Bacteria are reproductive experts.

75. 14. Some species of mushroom are edible.
15. The parasite is spread to humans and other
domestic animals by the bite of an infected
mosquito.

76. Quiz #3
Lesson 4

77. I. Modified True or False.
1. Living things may be multicellular or
unicellular.
2. Unicellular organisms are mostly
invisible to the naked eye.
3. Microorganisms be seen through naked
eye.

78. 4. Micros are organisms that
cause diseases.
5. Pathogens means small.
6. Robert Hooke discovered
animalcules in a drop of
rainwater.

79. 7. Anton Van Leeuwenhoek developed
the Gram-stain technique.
8. Entamoeba histolytica is parasitic and
can cause amebic dysentery.

80. 9. Gram-positive bacteria are those that
retain the red crystal violet stain.
10. Fungi are decomposers.

81. 11. A bacterial colony is a group of the same
kind of bacteria growing together on a specific
culture medium placed on a petri dish.
12. Red tides produce toxins that kill much of
the coastal wildlife.
13. Bacteria are reproductive experts.

82. 14. Some species of mushroom are edible.
15. The parasite is spread to humans and other
domestic animals by the bite of an infected
mosquito.