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BIO 102 > Bacteria > Flashcards

Bacteria Flashcards

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Biology 101 flashcards
1
Q

What are bacteria

A

Prokaryotic unicellular organisms that do not have a membrane bound nucleus and membrane bound organelles. They are omnipresent

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2
Q

Characteristics of bacteria

A

1.Bacteria cell wall is composed of peptidoglycan ( protein, lipids and glucans).
2. They lack chloroplasts and the carbohydrates form reserves consist of granules of glycogen and oil
3. The nuclear materials are not enclosed in a nuclear membrane and some genera have flagella therefore can move.

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3
Q

Criteria for classifying bacteria

A
  1. Based on shape
  2. Based on flagellation
  3. Based on nutrition
  4. Based on respiration
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4
Q

Classification based on shape

A
  1. Cocci
  2. Bacilli
  3. Spirilla
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5
Q

The ___________________ determines the shape of a cell

A

Rigid bacterial cell wall

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6
Q

The cocci or bacilli may be _________

A

Joined to form colonies or filaments

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7
Q

What’re pleomorphic bacterial cells

A

They can exhibit a variety of shapes e.g arthrobacter

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8
Q

Cocci

A

This group of bacteria is spherical, ellipsoidal or bean shaped, and is subdivided into six groups
1.Micrococci
2. Diplococci
3. Streptococci
4. Tetracocci
5. Staphylococci
6. Sarcinae

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9
Q

Types of cocci

A
  1. Micrococci: cells are arranged singly or irregularly. Members are saprophytes that live in water and air.
  2. Diplococci: cells divide along one plane and remain attached in pairs. Examples include those that cause deadly diseases like: Pneumonia, Cerebral meningitis and Gonorrhoea
  3. Streptococci: Cells here divide in one plane and remain attached to form chains of different lengths. Some cause disease of humans.
  4. Tetracocci: cells divide in two planes and form group of four cells.
  5. Staphylococci: cells divide in several planes results in an irregular pattern, producing bunches of cocci. Some cause disease in man and animals
  6. Sarcinae: cells divide in three planes, in a regular pattern, producing a cuboidal arrangement of cells. They are often found in air.
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10
Q

Types of bacilli

A
  1. Diplobacilli: occur in pair
  2. Streptobacilli: occur in chains of different lengths
  3. Palisades: those that are not arranged in a regular pattern
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11
Q

Types of spirilla

A
  1. Spirillum: are coiled forms of bacteria which may be twisted e.g spirillum minus ( rat-bite fever )
  2. Vibrioses: are curve/ comma shaped e.g the virio comma which causes cholera
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12
Q

All spirilla have_____ , about _____ of the bacilli and ___________ number of cocci are flagellated

A

Flagella, half, a small number

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13
Q

In a polar arrangements

A

The flagella are attached at one or both ends of the cell.

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14
Q

Types of flagellation ( polar arrangements)

A

1.Monotrichous- with a single flagellum at one end of the cell e.g cholera vibrio
2. Lophotrichous- with small bunches or tuft of flagella emerging from one end e.g alcaligenes faecalis.
3. Amphitrichous- with one or more flagella at both poles of the cell e.g spirillum volutans
4. Peritrichous- flagella are dispersed randomly over the surface of the cell e.g colibacillium.
5. Atrichous bacteria lack flagellum

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15
Q

Nutrition in bacteria

A
  1. Autotrophic nutrition
  2. Heterotrophic nutrition
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16
Q

Photoautotrophic nutrition

A
  1. Photoautotrophic bacteria:
    They use sunlight as their source of energy to synthesize food. Unlike photosynthetic eukaryotic cells they do not split water to obtain reducing power.
    Oxygen is not evolved during bacterial photosynthesis
17
Q

Types of photoautotrophic nutrition

A
  1. Photolithotrops:
    - In this hydrogen donor is an inorganic substance.
    - In green sulphur bacteria ( e.g chlorobium) hydrogen sulphide ( H2S) is hydrogen donor. The chlorophyll is bacteriovirdin

Photo-organolithotrops:
- In this hydrogen donor is a organic acid or alcohol e.g purple non- sulphur bacteria ( e.g Rhodospirillum)

18
Q

chemoautotrophic bacteria

A
  • They do not have photosynthetic pigments and hence they cannot use sunlight energy
  • They obtain energy in the form of ATP by oxidizing inorganic or organic compounds.
  • The energy this obtained is used to reduce CO2 to organic matter.
19
Q

Types of chemoautotrophs

A

Chemolithotrophs:
-Inorganic compound in oxidized to release energy.
- e.g sulphur bacteria ( e.g thiobacillus ) iron bacteria ( e.g Ferrobacillus ), hydrogen bacteria e.g Hydrogenomonas and nitrifying bacteria ( e.g Nitrosomonas and nitro bacter )

Chemo-organotrophs:
- An organic compound is oxidized to release energy. e.g methane bacteria ( methanococcus ) ; acetobacteria and lactobacillus

20
Q

Heterotrophic

A

They may be saprotrophic e.g ( bacillus subtilis) parasitic e.g Plant parasite ( xanthomonas citrii ) animal parasite e.g ( bacillus anthracis ) or symbiotic on association with roots of the family leguminosae e.g ( rhizobium )

21
Q

Respiration in bacteria

A

Aerobic bacteria:
- these bacteria require oxygen as a terminal acceptor of electrons and will not grow under anaerobic conditions ( in the absence of O2 )

Anaerobic bacteria:
- these bacteria do not use oxygen for growth and metabolism but obtain Thier energy from fragmentation reaction e.g clostridium sp

Facultative anaerobes:
- bacteria can grow either oxidatively using O2 as a terminal electron acceptor or anaerobically using fermentation reaction to obtain energy, bacteria that are facultative anaerobes are often termed “aerobes”
When s facultative anaerobes present at the site of am infection like an abdominal abscess it can rapidly consume all available O2 and change to anaerobic metabolism, producing an anaerobic environment and thus, allow the anaerobic bacteria that are present to grow and cause disease

Endospores: are structures formed in bacillus bacteria during unfavorable conditions. Fortunately most pathogenic bacteria do not form endospores

22
Q

Reproduction in bacteria

A

Reproduction by binary fission is very common, the other form of reproduction is sexual reproduction

23
Q

Sexual reproduction methods

A

Typical sexual reproduction involving the formation and fusion of gametes is absent in bacteria
However, Gene’s recombination can occur in bacteria by three different methods
- Conjugation
- Transduction
- Transformation

24
Q

Explain Conjugation

A

-In this method of gene transfer, the donor cell gets attached to the recipient cell with the help of pili
- The pilus grows in size and forms the conjugation tube
- The plasmid of donor cell which has the F+ ( fertility factor ) undergoes replication
- Only one strand of DNA is transferred to the recipient cell through the conjugation tube.
- The recipient completes the structure of double DNA by synthesizing the strand that compliments the strand acquired from the donor

25
Q

Explain Transduction

A

Donor DNA is carried in a phage coat and is transferred into the recipient by the mechanism used for phage infection

26
Q

Explain Transformation

A

-The direct uptake of donor DNA by the recipient cell may be natural or forced
-Relatively few bacterial species are naturally competent for transformation
-These species assimilate donor DNA in linear form
-Forced transformation is induced in the laboratory, where after treatment with high salt and temperature shock many bacteria are rendered competent for the assimilation of extra-cellular plasmids
-The capacity to force bacteria to incorporate extra-cellular plasmids by transformation is fundamental to genetic engineering

27
Q

Diseases caused by bacteria in animals

A

Sheep- Anthrax (Bacillus anthracis)
Cattle- Brucellosis (Brucella abortus)
Sheep, goat- Brucellosis (Brucella melitensis)

28
Q

Diseases caused bacteria in plant

A

Citrus- Citrus Canker (Xanthomonas citrii)
Rice- Bacterial blight (X. oryzae)
Cotton- Angular leaf spot (X. malcacearum)
Pears- Fire blight (Pseodomonas solanacearum)
Carrot- Soft rot (Erwiinia caratovora)

29
Q

Diseases caused by bacteria in humans

A

Cholera- Vibrio cholerae
Typhoid- Salmonella Typhi
Tuberculosis- Mycobacterium tuberculosis

30
Q

Benefits of bacteria

A

-Organic matter of sewage is decomposed by saprotrophic bacteria
-Saprotrophic bacteria cause decay and decomposition of dead bodies of plants and animals.
-Ammonia bacteria like Bacillus ramosus and B. mycoides convert complex proteins in dead bodies of plants and animals into ammonia which is later converted into ammonia which is converted into ammonium salts.
-The nitrifying bacteria such as nitrobacter, Nitrosomonas convert ammonium salts into nitrites and nitrates while nitrogen fixing bacteria such as Azotobacter, Closttridium and Rhizobium are capable of converting atmospheric nitrogen into organic nitrogen into organic nitrogen.
-The fibres from the fibre yielding plants are seperated by the section of bacteria like Clostridium species. This is called retting of fibres

BIO 102 (2 decks)

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