Chapter 4. Bacteria (the first microbes)

Chapter 4. Bacteria (the first microbes)

- the first microbes on earth -> prokaryotes (pro + karyo)

- bacteria are everywhere

-> 태평양 해구 바닥, 에베레스트 산봉우리, 사막, 북극의 빙하, 유황온천 -> 한 주먹의 흙 속 : how many bacteria ?

- bacteria can do every work

-> decomposer : 구성성분의 재순환

-> nitrogen fixation -> 식물 protein 공급(필수아미노산) -> 축산물 -> biological factory : antibiotics, vitamin, acetone

-> change history : 콜레라, 흑사병, 장티푸스

미국 옐로우스톤 Park

Chapter 4. Bacteria (the first microbes)

1. Bacterial structure and physiology

1) General morphology - three major forms

-> Bacillus(간균) : rod-shaped -> Coccus(구균) : spherical

-> Spiral(나선균) : spirochete -> rigid long, spiral spirillum -> flexible long, spiral

- vary in size : 0.5 μm ~ 750 μm (invisible organism?)

Chapter 4. Bacteria (the first microbes)

☞ different shape of cocci

- diplococci(쌍구균) : two cocci in group - tetrads(사련구균) : cocci in groups of four - sarcina(팔련구균) : cocci in groups of eight - streptococci(연쇄상구균) : cocci in chain - staphylococcus(포도상구균) : random cluster

A : Staphylococcus B : Streptococcus C : Bacillus

D : spirillum E : vivrio

Chapter 4. Bacteria (the first microbes)

2) Staining of bacteria

- most microbes are too small to be seen - bacterial cytoplasm is transparent

- fixation : 세포의 내 외부구조를 보존하여 slide에 부착

* 물리적 고정

- Slide에 세균 도말 -> 건조 -> 열처리 - 전체적 형태 유지, 내부구조 변형

* 화학적 고정

- 세포내부구조 형태 유지

- 화학고정액 사용-> 단백질, lipid, 탄수화물과 반응 -> 분자활성 정지

-> 불용화, 고정화

- Ethanol, Acetic acid, Formaldehyde, Glutaldehyde

- simple staining

- Gram staining : Gram positive, Gram negative

물리적 세균고정방법

(a)

Clostridium perfringens

(x800), (b)

Staphylococcus aureus

(x1000) (c)

Escherichia coli

(x500) (d)

Neisseria gonorrhoeae

(x1000)

Gram stained microorganism

Chapter 4. Bacteria (the first microbes)

☞ 다양한 원핵세포 모양

a: 방선균, b:무정형세균, c:나선균, d:균사형, e:네모형, f: 줄기형 부착기관

Chapter 4. Bacteria (the first microbes)

3) Surface Structure

(1) Cell wall : consisted of peptidoglycan layer -> thick(G+) or thin(G-) -> penicillin : protect synthesis of PG -> swell and burst

Figure 3.1d: Peptidoglycans can be held together by side chains to form the

cell wall of some types of bacteria.

Chapter 4. Bacteria (the first microbes)

Peptidoglycan layers of G⁺ and G^-

Chapter 4. Bacteria (the first microbes)

Effect of penicillin

Chapter 4. Bacteria (the first microbes)

(2) Cell membrane (plasma membrane) - phospholipid bilayer

- fluid mosaic model

Chapter 4. Bacteria (the first microbes)

(3) Glycocalyx

- capsule if tightly bound to the cell - slime layer if slimy and flowing - protection for bacterium

- shielding from drying, chemical, environmental stress - cling to surfaces -> dental caries

capsule, glycocalyx 구조

a) 염색된 capsule (Klebsiella pneumoniae) b) Bacteroides 의 glycocalyx

* 내장벽에 연결된 세균의 glycocalyx

Chapter 4. Bacteria (the first microbes)

(4) Flagellum

- rigid filament of protein

- rotates and propels a bacterium

- number changes according to species (5) Pilus

- hairlike structure, - 1μm long, 1nm thick - attaching to tissues or other surfaces

TEM of the heterotrophic bacterium Escherichia coli with pili (X40,000)

편모의 세부구조

a: Gram - b: Gram +

Chapter 4. Bacteria (the first microbes)

4) Cytoplasmic Structure (1) Chromosome

-> one, circular, tightly compacted DNA -> Nucleoid(핵양체) -> no protein involved (histone)

-> easy to manipulate

Chapter 4. Bacteria (the first microbes)

(2) Plasmid

-> tiny loops of DNA, suspended in cytoplasm -> replicate independently

-> encode nonessential cell proteins (several genes) -> important tools for modern DNA technology

(3) Necessary structures for protein synthesis -> ribosomes (rRNA + protein)

-> transfer RNA

-> organic substances

(carbohydrates, lipids, proteins, nucleotides)

Chromosome and Plasmid

Chapter 4. Bacteria (the first microbes)

(4) Spore (endospore)

-> unique form of bacterium formed when stress is encountered -> extraordinary resistant to stress

-> contains chromosome, two cell membrane, cortex, spore coat, exosporium ->

Bacillus

,

Clostridium

-> 250 million years old spore

-> bioterrorism ->

Bacillus anthracis

Structure of spore Vegetation of spore

Formation of bacterial spore

Chapter 4. Bacteria (the first microbes)

5) Bacterial Reproduction

- binary fission -> takes a few seconds

- replicates DNA to yield two identical chromosomes - one generation : 20 min for

E. coli

-> cover the face of the Earth a foot thick in 36 hrs -> last day of the world??

Chapter 4. Bacteria (the first microbes)

6) Bacterial Growth

- macronutrients : C, H, O, N, S, P, K, Ca, Mg, Fe - micronutrients : Mn, Zn, Co, Mo, Ni, Cu

- nutritional balance is important

- culture medium : source of energy, C, N, essential nutrients -> broth : liquid form vs agar : solid

- defined medium : all defined nutrients

- complex medium : contains undefined ingredients (yeast ext., peptone, beef ext.) - selective M : cultivate specific type of bacteria

- enriched M : require specific nutrients for growth, ex) blood agar

☞ pure culture : culture of a single species of microorganism

☞ colony : 동일한 미생물의 집단체 -> CFU (colony forming unit)

Use of an enriched medium

다양한 Colony 형태

Chapter 4. Bacteria (the first microbes)

미생물종류 에너지, 전자, 탄소원

광무기독립영양

Photolithotrophic autotroph

빛, 무기물, CO₂ (algae, cyanobacteria) 광무기종속영양

Photolithotrophic heterotroph

빛, 무기물, 유기탄소원

(Purple-nonsulfur bacteria, Green-sulfur bacteria)

광유기종속영양

Photoorganotrophic heterotroph

빛, 유기수소공여체, 유기탄소원 ( ? )

화학무기독립영양

Chemolithotrophic autotroph

화학무기물, 무기수소, CO₂

(Hydrogen bacteria, Sulfur-oxidizing bacteria, Iron bacteria)

화학유기종속영양

Chemoorganotrophic heterotroph

화학유기물, 유기수소공여체, 유기탄소원 (Protozoa, Fungi, nonphotosynthetic bacteria)

Mixotroph (혼합영양) 환경요인에 따라 대사양상변화

☞ 영양물질 이용에 따른 미생물 분류

Chapter 4. Bacteria (the first microbes)

7) Population Growth

- bacteria increase their population as the cells undergo binary fission

- growth curve : shows the growth of a microbial population over a period of time

Chapter 4. Bacteria (the first microbes)

☞ Doubling time(generation time) 결정

- 대수기에서 이분법으로 분열하는 세포수의 2배 증가 시간 N_o = 초기의 세포수

N_t = 시간 t 에서의 세포수 N_t = N_o x 2ⁿ n = t 시간 동안의 세대수

양변에 log를 취하면 -> log Nt = log No + n log2 n = = =

평균생장율상수 K = n/t (단위시간당 세대수) Log Nt - log No

Log 2

Log Nt - log No

0.301

Log Nt/No

0.301

Doubling time -> Nt = 2No 일 때의 시간 g로 표현 Log 2

0.301g

K = = 1/g g = 1/k

Log Nt/No

0.301t K =

K = Log N_t - log N_o 0.301t

Log 10⁹ - log 10³ (0.301)(10hr)

= = 2.0세대/hr

g = 1/k = hr/2.0 세대 = 30min/세대

Ex) 초기세포수 : 10³, 10시간 배양 후 세포수 10⁹일 때

Chapter 4. Bacteria (the first microbes)

8) Influencing factors for microbial growth

- water : microbial cytoplasm is water-based - temperature : influence enzyme reaction rate

-> psychrophiles : 0℃ ~ 20

℃

-> mesophiles : 20℃ ~ 45℃

-> thermophile : over 45℃

- oxygen : as electron acceptor

-> aerobic :require oxygen for their metabolism -> anaerobic : live only in the absence of oxygen

-> facultative : grow in the absence or presence of oxygen -> microaerophile : grow best in a low-oxygen environment - pH : acidophile -> grow in acid condition ex)

Helicobacter pylori

- halophile : inhabit high-salt environment

- barophile : high-pressure environment

Chapter 4. Bacteria (the first microbes)

Psychrophiles Thermophilic algae Hot spring

Acidophile,

Streptococcus lactis

^Halophiles Sulfurous lake

Chapter 4. Bacteria (the first microbes)

산소와 세균의 성장

- SOD(superoxide dismutase) : 2^·O₂^- + 2H⁺  H₂O₂ + O₂ - Catalase : 2H₂O₂  2H₂O + O₂

- O₂^-, H₂O₂ : toxic materials

Chapter 4. Bacteria (the first microbes)

2. Spectrum of Bacteria

1) Archaebacteria (Archaea)

- distinguished from traditional bacteria (eubacteria)

-> no peptidoglycan cell wall-> pseudopeptidoglycan

-> unusual lipid composition of cell membrane (ether linkage)

-> unique chemical composition of RNA (70S but different structure) -> habitat in extremely harsh environments => extremophiles

- thermoacidophiles : ex) 85℃, pH 1.0,

Sulfolobus acidocaldarius

ex) 113℃ flourish, not grow at 90℃,

Pyrolobus fumarii

- methanogens :

-> live solely on CO₂, N₂, H₂O -> produce methane under O₂-free cond.

-> volcanic rock, marshes, lake bottom, animal feces - extreme halophiles : Great salt lake

Chapter 4. Bacteria (the first microbes)

화석화된 세균 a: 35억년전 암석, b: 15억년전 우랄산맥 탄소암에서 발견(

Gloeodiniopsis

), c: 9.5억년전 동부시베리아(

Palaeolyngbya

)

Chapter 4. Bacteria (the first microbes)

유황온천, Yellowstone A:

Sulfolobus

, 60℃, pH 1.5-3, MoS₂ B:

Thermoproteus

의 전자현미경사진

Chapter 4. Bacteria (the first microbes)

2) Photosynthetic bacteria

- cyanobacteria(blue-green algae) :

-> chlorophyll pigments dispersed in cytoplasm

-> photosynthesis to produce organic material -> autotrophic microbes -> use sulfur extensively in their chemical reaction

-> carry out nitrogen fixation to produce NH₃, other N-containing substances

3) Heterotrophic eubacteria

- most species of so-called bacteria

- key players in global cycling of N, S, Fe, P, other nutrients - act as decomposers and producers

->

Azotobacter, Rhizobium

nitrogen fixation -> synthesis organic compounds -

E. coli

: human intestine, help new-born digest milk, tools for BT research

-

Lactobacillus

: female genital tract, guard against microbial infection, dairy product -

Pseudomonas aeruginosa, Serratia marcescens

: human pathogens

Chapter 4. Bacteria (the first microbes)

부영양화된 호수와 다양한

Cyanobacteria

Hot spring

Chapter 4. Bacteria (the first microbes)

Rhizobium

과 뿌리혹 형성

Chapter 4. Bacteria (the first microbes)

4) Spiral and filamentous bacteria - spiral bacteria ; resembles spring

-> Spirilla : flexible cells, flagella at the ends of the spiral

-> Spirochetes : rigid cells, long flagella inserted beneath the outer membrane - filamentous bacteria (actinomycetes : actino -> radiating, mycetes -> fungus)

-> long, chain-like branching

->

Streptomycetes

: produce numerous antibiotics

Spirochetes Spirillum

Chapter 4. Bacteria (the first microbes)

Filamentous bacteria

Chapter 4. Bacteria (the first microbes)

5) Gliding and sheathed bacteria

- produce slimy substances, then move by gliding along in it -

Beggiatoa, Thiothrix

: live in sulfur-rich muds

-> release sulfur which can be reusable

- myxobacteria : have unique developing cycle forming fruiting bodies when nutrients are exhausted

- sheathed bacteria : a type of filamentous bacteria having cell walls enclosed in a sheath of complex carbohydrates and protein

-> protect the bacteria from stress

-> permits the bacteria to attach to food particle -> ex)

Sphaerotilus

Chapter 4. Bacteria (the first microbes)

Myxococcus

의 fruiting body, spore 및 생활주기

Chapter 4. Bacteria (the first microbes)

6) Predatory and other bacteria

- Bdellovibrios : rod-shaped bacteria that prey on other bacteria -> rotates and bores a hole cell wall -> kill host

->

Bdellovibrio bacteriovorous

- Bacteroides : Gram-, rod, live on O₂-free environment

-> in the stomach of cow -> digest cellulose in plant cell -> 30% of the bacterial mass of human feces

- Chemolithotrophic bacteria : inorganic substance as electron donor ->

Nitrosomonas, Nitrobacter

: use nitrate, nitrite

-> essential feature of cycle of nature

Chemolithotrophic bacteria와 에너지원

Predatory bacteria의 먹이 공격

Amoebophilus

 아메바 안에서 증식하는 박테리아

 아메바 안으로 들어가기 위한 세

포막 통과에 스프링이 달린 단검 같은 구조물 사용 -> 여러 개의 원 통형 구조물이 갑자기 튀어나오면 서 세포막을 뚫음 -> 단검보다는 죽창에 더 가까운 구조물

 침입 후 : 아메바의 소화 기관이 이 를 인지하고 소화시키기 위해 공 격 -> 소화효소를 무력화시킬 수 있는 화학 물질 생산 -> 아메바 안 에서도 소화되지 않을 뿐 아니라 증식까지 가능.

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