Transcript Cell Wall

Estrutura e função da célula
procariotica
Cell Diagram: Mariana Ruiz, pub domain
a BIOMASSA DE BACTERIAS NA TERRA É ESTIMADA A
SER IGUAL QUE A DE PLANTAS. O NUMERO DE
PROCARIOTES NA TERRA ESTIMADO É DE 5 × 1030,
QUE REPRESENTA A METADE DA BIOMASSA GLOBAL.
^ Whitman W, Coleman D, Wiebe W (1998). "Prokaryotes:
the unseen majority". Proc Natl Acad Sci USA 95 (12):
6578–83. doi:10.1073/pnas.95.12.6578. PMC 33863.
PMID 961845
HABITAT
pH ácido
pH alcalino
Outros habitats
Arvore universal da vida derivada do sequenciamento de ssRNA.
N. Pace
Arvore universal da vida derivada do sequenciamento de ssRNA.
N. Pace
--Archaea are the least evolved type of
cell (they remain closest to the common
point of origin). This helps explain
why contemporary Archaea are
inhabitants of environments that are
something like the earth 3.86 billion
years ago
(hot, salty, acidic, anaerobic, low in
organic material, etc.) Ref. Todar
microbiology.
Metano e CO2= origem do efeito estufa-aquecimento da terra
Size of Living Things
1 m = 100 cm = 1,000mm = 1,000,000 µm = 1,000,000,000nm
1mm = 1000 µm = 1000000nm
1 µm = 1000nm
Diagrams: http://www.cellsalive.com/howbig.htm
Tamanho da célula bacteriana
Célula típica: diametro 1 - 2
μm (~ tamanho de
mitocôndria)
Megabactéria (Epulopiscium
fishelsoni): 80 x 600 μm,
portanto visível ao olho nú
Nanobactéria
Streptooccus pneumoniae
Bacillus antrax=bacteria gram +
E. coli
E. coli durante a conjugação
-E. coli - Gram-negative, facultatively anaerobic, rod prokaryote; strains undergoing conjugation, one strain has fimbriae.
- E. coli can cause urinary tract infections, traveler's diarrhea and nosocomial infections.
File Name:-- 71241JWA
Category:-- Bacteria Type of Image:-- TEM
Magnification:-- x3,645--(Based on an image size of 1 inch in the narrow dimension)
Two basic types of cells
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Diagrams:
Prokaryotic & Eukaryotic Cell, Mariana Ruiz
Prokaryotes – Cell Wall
Peptidoglycan is a huge polymer of interlocking chains of
identical peptidoglycan monomers.
Backbone of peptidoglycan molecule composed of two
derivatives of glucose:
N-acetylglucosamine (NAG)
N-acetlymuramic acid (NAM)
NAG / NAM strands are connected by interpeptide bridges.
Peptidoglycan
- Rigid mechanical support
- Freely permeable to solutes
Image:
Peptindoglycan Structure: NicolasGrandjean
Prokaryotes - Cell Wall: Gram-Negative & Gram-Positive
Image:
Prokaryotic Cell, Mariana Ruiz
Gram +-, Julian Onions
N-acetil glucosamina e acido
muramico
Chapter 4
Cell Wall
• Peptido-glycan Polymer (amino acids +
sugars)
• Unique to bacteria
• Sugars; NAG & NAM
– N-acetylglucosamine
– N-acetymuramic acid
• D form of Amino acids used not L form
– Hard to break down D form
•Chapter
Amino
acids cross link NAG & NAM
4
Video Clip parede celular
Chapter 4
Chapter 4
Cell Wall Summary
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Determine shape of bacteria
Strength prevents osmotic rupture
20-40% of bacteria
Unique to bacteria
Some antibiotics effect directly
– Penicillin
Chapter 4
Why are these differences
in cell wall structure so
important?
Images: Sources unknown
Prokaryotes - Glycocalyx
Some bacteria have an
additional layer
outside of the cell wall
called the glycocalyx.
This additional layer can
come in one of two
forms:
1. Slime Layer
2. Capsule
STRUCTURE OF MICOBIAL CELLS
Prokaryotes - Glycocalyx
Some bacteria have an additional layer outside of the cell wall
called the glycocalyx.
This additional layer can come in one of two forms:
glycoproteins loosely associated with the cell wall.
Slime layers cause bacteria to adhere to solid surfaces and help
prevent the cell from drying out.
Streptococcus
The slime layer of Gram+ Streptococcus mutans allows it to
accumulate on tooth enamel (yuck mouth and one of the causes of
cavities).
Other bacteria in the mouth become trapped in the slime and form
a biofilm & eventually a buildup of plaque.
Staphylococcus
The slime layer of Gram+ Staphylococcus allows it to thrive in the
salty, hypertonic environment of the skin.
Glycocalyces are not specific to Gram+ or Gram- bacteria,
sometimes only some members of a certain species (strains) have a
glycocalyx, whereas others don’t.
STRUCTURE OF MICOBIAL CELLS
Prokaryotes - Glycocalyx
Capsules adhere to solid
surfaces and to nutrients in the
environment.
Adhesive power of capsules is a
major factor in the initiation of
some bacterial diseases. Capsule
also protect bacteria from being
phagocitized by cells of the
hosts immune system.
STRUCTURE OF PROKAROTIC CELLS
Prokaryotes - Glycocalyx
Bacterial Capsule and Meningococcal Infection
Meningococcal infection is caused by meningococcal
bacteria (Neisseria meningitidis).
Causes:
1.
meningococcal meningitis (infection of the
meninges/spinal cord)
2.
meningococcal septicaemia (blood poisoning).
Of the two forms, meningococcal septicaemia is the
most dangerous.
Meningococcal bacteria are the most common cause
of bacterial meningitis.
Meningococcal bacteria grow
in pairs called diplococci often
surrounded by a capsule coat.
Over a million of these would
fit on the head of a pin.
Approximately 5% of people who suffer from
meningococcal meningitis will die.
http://www.meningitisuk.org/about-meningitis/bacterial-meningitis.htm
STRUCTURE OF PROKAROTIC CELLS
Prokaryotes - Endospores
Dormant, tough, non-reproductive
structure produced by small
number of bacteria.
Primary function of endospores:
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Resistant to radiation,
desiccation, lysozyme,
temperature, starvation, and
chemical disinfectants.
A stained preparation of Bacillus
subtilis showing endospores as green
and the vegetative cell as red
Endospores commonly found in soil
and water, where they may
survive for long periods of
time.
Image:
Stain: Jerry Keplinger, James H. Quillen College of Medicine
Procedure: Source link no longer works
STRUCTURE OF PROKAROTIC CELLS