Bacteria
large group of unicellular, prokaryotes, bacteria.
The bacteria are usually more
, micrometers in length and have a wide range of forms from areas
rods and spirals (,
). Bacteria are widely distributed in each habitat
on earth, growing in soil, acidic hot
sources, radioactive waste, water and deep in the
crust, as well as organic matter and
, living bodies of plants and animals. There
usually 40000000 bacterial cells in one gram of soil and
million bacterial cells in a milliliter
Freshwater, everyone has
about five nonillion (5 ‡ 10
) >> << bacteria on Earth, forming much of the biomass >> worlds. Figure 1 <<. Bacteria are in many cellular forms. Figure 2. Most bacteria have a diameter in the range of 1
ET (micrometer) to 5 them. Left to right:
spherical (cocci), bacteria, bacillary (bacilli)
bacteria spiral bacteria. Bacteria are vital nutrients
processing, many steps in nutrient cycles
depending on these organisms, such as
fixing nitrogen from the atmosphere and
decay. However, most bacteria do not
characterized, and only about half
types of bacteria have species that can be grown in the lab
. The study of bacteria
known as bacteriology, microbiology department. There are about ten times more >> << bacterial cells in the human flora
bacteria as human cells in the body >> <<, with lots of bacteria on the skin and how to >> << intestinal flora. The vast majority of bacteria in the body
disposed protective effect on the immune system, and
little helpful. Bacteria
be profiled in this section are those
pathogenic to humans, causing infections
(
). Figure 3. Areas of the body that are prone
different types of bacteria. Click to enlarge. Gram-negative bacteria have relatively
thin cell wall consisting of several layers of peptidoglycan surrounded by
second lipid membrane containing strattera 25mg lipopolysaccharides and lipoproteins
(). These bacteria not
retain crystal violet dye in the Gram staining protocol
because of their lipopolysaccharides outer layer >>. In grams << test
contrasting color (usually safranina) is added after the crystal violet color
all gram-negative bacteria with
, red or pink. On the other hand,
positive bacteria retain the crystal violet dye
when washing in bleaching solutions >> << because they have no external >> << membranes, but rather they have thickened
peptidoglycan layer. illustrates the difference
to antigens associated with two
different types of bacteria. Figure 4. The outer surface of Gram-negative bacteria: Note
LPS in the outer membrane. Figure 5. Antigens involved in
host response to bacteria: Gram-positive and
gram-negative bacteria. Click to enlarge. Pathogenic features
Gram-negative bacteria often associated with some components
Gram-negative cell wall,
including lipopolysaccharides (also known as
LPS or endotoxin) layer (
). People
LPS can induce both innate and adaptive immune
,
response characterized by cytokine production and immune system
activation. For example, LPS can cause a cascade
supplement, which is part of the innate immune response
and bind to Toll-like receptors
(TLR-4) on B-lymphocytes to cause
adaptive, humoral response without
T-helper cells, thus, LPS is known as
T-independent antigens. Inflammation is a common result >> << cytokine production, which can also produce
host toxicity. Protection against gram-negative bacterial
infection: antibodies produced by B-lymphocytes, such as
immunoglobulin M (IgM) are effective against bacterial
extracellular pathogens. Antibodies
can protect against gram-negative bacteria
accession to the surface and activation of complement. Activated complement cascade induces the formation
in the membrane attack complex (MAC), which produces holes or pores in >> << outer membrane. Antibodies attached to >> << bacteria can also join such as phagocytes >> << macrophages through Fc receptors of phagocytes
process called
- opsonizatsiyi (
). It promotes phagocytosis
and bacterial removal. In addition, amendments related
bacteria can attach to phagocytes via complement receptors
(CR), which promotes phagocytosis
(
). Figure 6. Examples of antibody-mediated mechanisms against gram-negative bacterial
infection. A. Cytoplasmic membrane
2. A thin layer of peptidoglycan
(which is much thinner than that of gram-positive bacteria
)
3. Outer membrane containing lipopolysaccharides
(LPS consisting of lipid
main polysaccharides, as well as the antigen) outside the peptidoglycan layer
,
4. Porins exist in the external >> << membranes that act as pores for particular molecules
5. There is space between the
layers of peptidoglycan and secondary >> << cell membrane called Peryplazma
6. S-layer directly
attached to the outer membrane, not peptidoglycan
7. If present, flagella in
four supporting rings instead of two
8. No teyhoevye acid or acids lipoteyhoevaya
There are 9. Lipoproteins are added
on the polysaccharide backbone. 10. Most do not sporuliruyut
In general, cell wall
Gram-negative microorganisms are much more complex than
cell wall of gram-positive bacteria. From outside the membrane, it is
the following:
peptidoglycan layer two
nm in thickness, forming 5% of the cell wall
mass, often associated with outside
designing molecules lipoproteins
outer membrane consisting of a lipid bilayer, similar to >> << some respects to the membrane that
contains protein molecules and (on its inner aspect
) lipoproteins related
peptidoglycan. Other proteins form
transmembrane water-filled channels called
porynov by which hydrophilic antibiotics >> << are free to move. Complex polysaccharides
forming the outer surface of the major components >>. They differ << strains of bacteria and
main determinants of antigenicity. Complex polysaccharides >>
<< a source of endotoxin, which in vivo, trigger different
aspects of inflammatory response by activating complement
causing fever. Gram-negative bacillus E. coli E. coli E. coli Gram-negative cocci Neisseria g onorr hoeae.
,
