THE MAIN FORMS OF BACTERIA,MORPHOLOGY, ULTRASTRUCTURE AND FUNCTIONS OF BACTERIA Flashcards
Spirochetes charactrise and how it achieve their motillity
- elongated, motile, flexible bacteria. The body consists from the hollow
coil which enclosed by the cytoplasmic membrane,
the outer membrane is the thin cell wall
. All spirochetes are actively motile and achieve their motility by means of two or more axial filaments
The axial filaments are enclosed by ,attached ,and (function and how)
in the space between an outer sheath and the body of the cell.
One end of each axial filament is attached near a pole of the cell on the disks-blepharoplasts.
By rotating its axial filament, the cell rotates in the opposite direction to move through liquids like a corkscrew
The main forms of bacteria: Morphologically bacteria possess three main forms:
- Spherical (cocci).
- Rod-shaped (bacteria bacilli and clostridia).
- Spiral shaped (vibrios and spirilla/.
A)cocci are subdivided according to—-
into six groups—–
according to plan of cell division, cell arrangement; and biological properties.
- Micrococci (micrococcus) - divide in one plane. The cells are arranged singly or irregularly. They are
saprophytes and live in water and in air. - Diplococci (GK-diplos-double) - divide in one plane and remain attached in pairs. These include:
meningococcus, causative agent of epidemic cerebrospinal meningitis and gonococcus causative agents of gonorrhoea and blennorrhoea. These cocci resemble coffee bean. Another diplococcus is pneumococcus –
the causative agent of pneumonia. This diplococcus looks like a lancet - Streptococci (GK–Streptos-chain) divide in one plane and are arranged in chains of different length.
They are probably responsible for a number of illnesses and cause a greater variety of diseases than any
other group of bacteria. Scarlet fever, pharyngitis (sore throat) and others are among the diseases caused
by streptococci. - Tetracocci (GK–tetra–four) divide in two planes and form groups of fours. They are saprophytes.
- Sarcinae (GK-Cartio-to tie) - divide in three planes and resemble packets of 8, 16 or more cells. They are frequently found in the air. These are conditionally pathogenic organisms.
- Staphylococci (GK–Staphyle–cluster of grapes) - divide in several planes resulting in irregular bunch of cells, sometimes resembling clusters of grapes. The most important staphylococcal species is
S. aureus,
named for its yellow pigmented colonies (aureus means golden), causative agents of diseases in man and animals. S. aureus produced many toxins that contribute to the bacterium’s pathogenicity by increasing its
ability to invade the body or damage tissue
- Diplococci (GK-diplos-double) - divide in —- and remain attached in pairs.
These include:
——–, causative agent of ———-
and ———-causative agents of ——and —–.
These cocci resemble coffee bean.
Another diplococcus is ———— –
the causative agent ———- . This diplococcus looks like a lancet
- Diplococci (GK-diplos-double) - divide in one plane and remain attached in pairs. These include:
meningococcus, causative agent of epidemic cerebrospinal meningitis and gonococcus causative agents of
gonorrhoea and blennorrhoea. These cocci resemble coffee bean. Another diplococcus is pneumococcus –
the causative agent of pneumonia. This diplococcus looks like a lancet.
- Streptococci (GK–Streptos-chain) divide in —— and are arranged in —–
They are probably responsible for a number of illnesses and cause a greater variety of diseases than any other group of bacteria. —, —– and others are among the diseases caused
by streptococci.
- Streptococci (GK–Streptos-chain) divide in one plane and are arranged in chains of different length.
They are probably responsible for a number of illnesses and cause a greater variety of diseases than any other group of bacteria. Scarlet fever, pharyngitis (sore throat) and others are among the diseases caused
by streptococci.
- Staphylococci (GK–Staphyle–cluster of grapes) - divide in ——resulting in irregular bunch
of cells, sometimes resembling clusters of grapes. The most important staphylococcal species is ——
named for its ———– (aureus means golden), causative agents of diseases in man and
animals. S. aureus produced many toxins that contribute to the bacterium’s pathogenicity by increasing its ability to invade the body or damage tissue
- Staphylococci (GK–Staphyle–cluster of grapes) - divide in several planes resulting in irregular bunch of cells, sometimes resembling clusters of grapes. The most important staphylococcal species is
S. aureus,
named for its yellow pigmented colonies (aureus means golden), causative agents of diseases in man and animals. S. aureus produced many toxins that contribute to the bacterium’s pathogenicity by increasing its
ability to invade the body or damage tissue
***** B)Rods - rod-shaped or cylindrical forms are subdivided into bacteria (include those micro-organisms
which as a rule do not produce spores – e.g. organisms responsible for enteric fever-paratyphoids,
dysentery, diphtheria, etc.) bacilli and clostridia (spindle form) include organisms the majority of which
produce spores (e.g. bacilli responsible for anthrax, clostridia - tetanus, and etc.). Bacillus (B. anthracis) is
rod shape spore forming aerobic microorganism. Clostridium (C. tetani, C. botulinum) are rod shape,
spore forming, anaerobic microorganisms. Rods exhibit differences in the form of ends, in shape and size
as well as in arrangement. By the form of end they may be rounded, pointed, thickened, truncated, etc..
By size they may be small (0.5-1.5µm) middle (2-5µm) and large (6-10µm). By their arrangement they
may be irregular arranged, in pairs, in chains.
Rods - rod-shaped or cylindrical forms are subdivided into bacteria (include those micro-organisms
which as a rule do not produce spores – e.g. organisms responsible for enteric fever-paratyphoids,
dysentery, diphtheria, etc.) bacilli and clostridia (spindle form) include organisms the majority of which
produce spores (e.g. bacilli responsible for anthrax, clostridia - tetanus, and etc.). Bacillus (B. anthracis) is
rod shape spore forming aerobic microorganism. Clostridium (C. tetani, C. botulinum) are rod shape,
spore forming, anaerobic microorganisms. Rods exhibit differences in the form of ends, in shape and size
as well as in arrangement. By the form of end they may be rounded, pointed, thickened, truncated, etc..
By size they may be small (0.5-1.5µm) middle (2-5µm) and large (6-10µm). By their arrangement they
may be irregular arranged, in pairs, in chains.
C) Spiral shaped bacteria ––, —– and ——– belong to this group of bacteria.
Spirills are -----forms of bacteria exhibiting-----------. Only one pathogenic species is known (-----) which is responsible for a disease in humans, transmitted through ------------.
Vibrions, Spirilla and Spirochetes belong to this group of bacteria.
Spirills are coiled forms of bacteria exhibiting twists with one or more turns.
Only one pathogenic species is known (Spirillum minus) which is responsible for a disease in humans, transmitted through the bite of
rats and other rodents (Sodoku).
Bacteria differ essentially from plant and animal cells in structure.
They consist of the main and supplementary (additional) structures:
The main structures are: —
The supplementary (additional) structures are:
The main structures are
cell membrane
cytoplasm
nucleoid
The supplementary (additional) structures are:
flagella
pili (fimbriae)
Spores
The cell membrane consists of three components:
- the external layer – glycocalyx which may form a capsule
- the middle layer – cell wall
- the internal layer – cytoplasmic membrane
CAPSULE(the external layer) - glycocalyx is a viscous (sticky), gelatinous polymer that is external to
the cell wall and
is composed ——–
Its chemical composition varies widely with the species. This external layer can take the form of capsule in some bacteria.
Capsule usually forms in human or animal organisms (—-,—–), but some bacteria can form capsule in nutrient media too (eg. —–,—–,—)
which called constantly capsule forming bacteria (capsular). The capsule is composed of: polysaccharides (---------, ------------------); polypeptides (----------------, -----------). Capsule forming bacteria are:1-8 1.Streptococcus pneumonia -------------
is composed of polysaccharide, polypeptide, or both
Capsule usually forms in human or animal organisms (B. anthracis, S. pneumonia, etc.), but some bacteria can form capsule in nutrient media too (eg. K. pneumonia, K. ozenae, K. rhinoscleromatis
The capsule is composed of: polysaccharides (Streptococcus pneumonia, Clostridium perfringens); polypeptides (Bacillus anthracis, Yersinia pestis). Capsule forming bacteria are: 1.Streptococcus pneumonia 2.Clostridium perfringens 3.Klebsiella pneumonia 4.Klebsiella ozenae 5.Klebsiella rhinoscleromatis 6.Neisseria. meningitis 7.Bacillus anthracis 8.Yersinia pestis
Capsule cannot be stained with ordinary stains like gram staining.
It can be visualized by———-, ———- staining methods and it may also be visualized by ———————(capsular material is antigenic and may be demonstrated by serological methods)
which causes a characteristic swelling of the capsule. It is known as ——. This phenomenon is seen in and allows rapid identification of capsular —— of ——–, ———- and etc.
1.Protective: protection of microorganism from biological, physical, chemical agents (phagocytosis,
antibodies, antibacterial drugs, drying.)
2.Virulence: it is determinant of virulence of many bacteria, since it limits the ability of phagocytes to
engulf the bacteria. Loss of the capsule may render the bacterium avirulent.
3.Antigenicity: capsular polysaccharides and polypeptides ensure the antigenicity.
4.Adhesive: The capsule may play a role in the adherence of bacteria to human tissues, which is an
important initial step in causing infection.
Capsule cannot be stained with ordinary stains like gram staining.
It can be visualized by Ionne, Burry-Hins staining methods and it may also be visualized by reaction
with specific antibody(capsular material is antigenic and may be demonstrated by serological methods)
which causes a characteristic swelling of the capsule. It is known as Quellung reaction. This
phenomenon is seen in and allows rapid identification of capsular serotypes of Streptococcus
pneumoniae, Neisseria meningitidis and etc.
CELL WALL (the middle layer) - the bacterial cell wall is composed of a macromolecular network called ———— (—–) which consists of————- and———— which are combined with —– bonds.
NAM includes tetrapeptide side chains,
which consist of four amino acids: ——-, ———-, ———- and —————- – which is
found only in bacteria cell. These tetrapeptides are combined with ——— bonds.
Since peptidoglycan is present in bacteria but not in human cells, it is a good target for antibacterial
drugs. Such as inhibited synthesis of cell wall.
The enzyme lysozyme, which is present in human tears, mucus and saliva, can cleave the peptidoglycan
backbone by breaking its ——-, thereby contributing to the natural resistance of the host to
microbial infection.
CELL WALL (the middle layer) - the bacterial cell wall is composed of a macromolecular network called peptidoglycan (murein) which consists of N-acetyl glucosamine (NAG) and N-acetylmuramic acid (NAM) which are combined with glycosyle bonds. NAM includes tetrapeptide side chains,
which consist of four amino acids: D-alanine, L-alanin, D-glutamine and diaminopimelic acid which is
found only in bacteria cell. These tetrapeptides are combined with peptide bonds.
Since peptidoglycan is present in bacteria but not in human cells, it is a good target for antibacterial
drugs. Such as penicillins and cephalosporins, inhibited synthesis of cell wall.
The enzyme lysozyme, which is present in human tears, mucus and saliva, can cleave the peptidoglycan
backbone by breaking its β-glycosyle bonds, thereby contributing to the natural resistance of the host to
microbial infection.
CELL WALL (the middle layer) The structure, chemical composition and thickness of the cell wall differ in ------- and g--------.
In most gram-positive bacteria, the cell wall——–,forming a —–, —–
(by contrast, gram-negative cell walls contain———)..
It constitutes 50-90% of the dry weight of the cell wall.
The cell wall of gram-positive bacteria contains ——, which is ———or ——
The structure, chemical composition and thickness of the cell wall differ in gram-positive and gramnegative bacteria. In most gram-positive bacteria, the cell wall consists of many layers of peptidoglycan,
forming a thick, rigid structure (by contrast, gram-negative cell walls contain only a thin layer of peptidoglycan). It constitutes 50-90% of the dry weight of the cell wall. The cell wall of gram-positive bacteria
contains teichoic acid, which is ribitol or glycerol polymers.
