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Microbiology Exam 1 > Microbial Metabolism, Structure, and Function > Flashcards

Microbial Metabolism, Structure, and Function Flashcards

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1
Q

What kind of DNA do bacteria have?

A

One circular chromosome, composed of double-stranded DNA, located in the Nucleoid

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2
Q

When are bacteria most susceptible to antimicrobials?

A

During the Lag Phase and the Exponential Phase

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3
Q

When are bacteria less susceptible to antimicrobials?

A

Stationary phase

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4
Q

What phase does sporulation occur in?

A

Stationary phase

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5
Q

What phase is the bacteria actively metabolizing?

A

Exponential phase

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6
Q

What are the minimum requirements for growth?

A

A source of carbon and nitrogen, an energy source, water, and various ions

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7
Q

What four factors determine growth in culture?

A

pH optimum
Aerobic vs anaerobic
Nutrients/composition of media
Temperature

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8
Q

How is cell density determined?

A

Colony counts on agar plates or by turbidity using spectophotometry

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9
Q

Aerobic Bacteria

A
  • Exclusively use respiration to meet energy needs

- E.g. M. tuberculosis, P. aeroginosa, B. anthrasis

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10
Q

Anaerobic Bacteria

A
  • Exclusively use fermentation to meet energy needs
  • E.g. C. botulinum, Bacteriodes
  • **Much LESS efficient than respiration
  • Will be KILLED BY OXYGEN
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11
Q

Facultative anaerobes

A

Can respire or ferment

E.g. E. Coli, Shigella dysenteriae, S. aureus

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12
Q

Microaerophilic

A

Grow best at low oxygen but can grow without it as well

E.g. C. jejuni

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13
Q

How do bacteria counteract the highly reactive forms of oxygen (e.g. Hydrogen Peroxide H2O2 and Superoxide Anion O2-)?

A
  • Catalase (catalyzes the breakdown of H2O2 to H2O and O2)

- SOD (Superoxide Dismutase; expressed by both prokaryotes and eukarotes to detoxify O2-)

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14
Q

Bacteria that lack SOD and Catalase are…

A

Sensitive to oxygen and likely Anaerobic

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15
Q

Fermentation

A

Pyruvate is converted to various end products, which then can be used to identify bacteria in the lab

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16
Q

5 targets of antibiotics

A
  1. Cell wall synthesis
  2. DNA replication
  3. RNA synthesis
  4. Protein synthesis
  5. Antimetabolites
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17
Q

Nucleic Acid Biosynthesis: Nucleotide Uses

A

Building blocks of DNA and RNA, ATP and GTP, cofactors (NAD, FAD, coenzyme A), biosynthetic intermediates (UDP-glucose), and second messengers (cAMP, cGMP)

18
Q

Folate is essential in the synthesis of…

A

Purines and Thymidine

19
Q

Why is folic acid a good target for bacterial toxicity?

A

Bacteria derive their folic acid from para-aminobenzoic acid (PABA), while mamalian cells use pre-formed folate from the diet

20
Q

What enzyme do Sulfonamides act on?

A

Dihydropteroate synthase (DHPS); NOT present in mammals

21
Q

What enzyme does Trimethoprim act on?

A

Dihydrofolate reductase (DHFR); present in mammals, but DIFFERENT

22
Q

Binary Fission: what unwinds bacterial DNA?

A

Bacterial DNA gyrase

23
Q

What targets bacterial DNA gyrase?

A

Quinolones

24
Q

What is different about transcription/translation in bacteria?

A

They are coupled (Co-Transcriptional Translation) as they do not have a nucleus

  • 70s ribosomes (vs. 80s in eukoaryotes) binds free 5’ end of mRNA as DNA is transcribed
  • Multiple ribosomes are bound to mRNA forming a polyribosome
25
Q

Structure of Peptidoglycan in E. coli

A

Bond DAP of the peptide in one chain to the Ala at position FOUR of an adjacent chain

26
Q

General structure of a Peptidoglycan

A

Peptides are cross-linked through a peptide bond between the terminal D-Alanine from one chain and a Lysine (or other diamino acid) from the other chain

27
Q

Other names for N-acetylglucosamine

A

NAG, GlcNAc, G

28
Q

Other names for N-acetylmuramic acid

A

NAM, MurNAc, M

29
Q

Step 1 of Cell Wall Biosynthesis

A

Activation of carbohydrate subunits with UDP

30
Q

Step 2 of Cell Wall Biosynthesis

A

A pentapeptide is added to UDP-NAM

***Important: this step is INDEPENDENT of mRNA and ribosomes; it is produced ENZYMATICALLY

31
Q

What is the order of the amino acids coming off NAM-UDP?

A

L-ala (variable)— D-glu (variable) — L-lys (diamino acid; Lysine, diaminopilemic acid) — D-ala — D-ala

***The D-ala’s do not change; they are important in cross-linking

32
Q

Step 3 of Cell Wall Biosynthesis

A

UDP-NAM-pentapeptide is attached to the BACTOPRENOL through a pyrophosphate link with the release of UMP

33
Q

What is Bactoprenol?

A

Lipid carrier found in the cytoplasmic membrane

34
Q

Step 4 of Cell Wall Biosynthesis

A

NAG is added to NAM-pentapeptide-bactoprenol complex

35
Q

Step 5 of Cell Wall Biosynthesis

A

The bactoprenol carrier transports the completed NAG-NAM pentapeptide repeat unit across the membrane

36
Q

Step 6 of Cell Wall Biosynthesis

A

The disaccharide unit is attached to the end of the growing peptidoglycan chain by enzymes called TRANSGLYCOSYLASES

37
Q

Step 7 of Cell Wall Biosynthesis

A

Pyrophosphobactoprenol is converted to phosphobactoprenol and recycled

38
Q

What is the mechanism of Vancomycin?

A

Prevents Penapeptide-NAM-NAG from attaching to Peptidoglycan

39
Q

What is the mechanism of Bacitracin?

A

Prevents Bactoprenol from crossing the membrane

40
Q

Peptidoglycan synthesis - Outer leaflet of cell membrane: Transpeptidation

A

Occurs between the free amine of the diamino acid in the 3rd position of the pentapeptide (or the N-terminus of the attached pentaglycine chain) and the D-alanine at the 4th position of the other peptide chain, RELEASING THE D-ALANINE PRECURSOS

41
Q

Transpeptidases

A

Mediate transpeptidation reaction

-Also called Penicillin Binding Proteins (PBP) because they are targets for penicillins and other B-lactam antibiotics

Microbiology Exam 1 (11 decks)

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