C4 Flashcards
Cellular microbes
(bacteria, archaea, algae, protozoa, and
fungi)
acellular microbes or infectious particles
(viruses, viroids,
and prions)
four categories of viruses
*Double-stranded DNA viruses
*Single-stranded RNA viruses
*Single-stranded DNA viruses
*Double-stranded RNA viruses
Some viruses cause specific types of cancer
oncogenic viruses or oncoviruses
A typical virion consists of a genome of either DNA or
RNA, surrounded by a capsid (protein coat), which is
composed of protein units called
capsomeres
Viruses that infect bacteria are known as
bacteriophages
or simply phages
There are two categories of bacteriophages
virulent bacteriophages and temperate bacteriophages.
always cause what is known as
the lytic cycle, which ends with the destruction of the
bacterial cell
Virulent bacteriophages
The five steps in the lytic cycle
attachment,
penetration,
biosynthesis,
assembly,
release.
Steps in the multiplication of animal viruses are
- Attachment
- Penetration
- Uncoating
- Biosynthesis
- Assembly
Viral infections in which the virus is able to hide from a host’s immune system by entering cells and remaining dormant.
– Herpes viral infections are examples.
Latent virus infections
are drugs that are used to treat
viral infections.
Antiviral agents
This virus causes acquired immunodeficiency syndrome
(AIDS).
– It is an enveloped, single-stranded RNA virus
Human immunodeficiency virus (HIV)
These viruses cause cancer.
Oncogenic viruses or oncoviruses
are short, naked fragments of single stranded RNA, which can interfere with the metabolism of plant cells
Viroids
are small infectious proteins that
cause fatal neurologic diseases in animals and humans (e.g., Scrapie, bovine spongiform encephalopathy [mad cow disease], and Creutzfeldt–Jacob disease)
Prions
Bacteria are divided into three major phenotypic categories
– Those that are Gram-negative and have a cell wall
– Those that are Gram-positive and have a cell wall
– Those that lack a cell wall (Mycoplasma spp.)
There are three basic categories of bacteria based on
shape:
– Cocci (round bacteria)
– Bacilli (rod-shaped bacteria
– Curved and spiral-shaped bacteria
They are often referred to as rods; they may be short or long, thick or thin, and pointed or with curved or blunt
ends.
– They may occur singly, in pairs (diplobacilli), in chains
(streptobacilli), in long filaments, or branched.
Bacilli
Examples of medically important bacilli:
Escherichia, Klebsiella, Proteus,
Pseudomonas, Haemophilus, and Bacillus spp.
Extremely short bacilli are called
coccobacilli
not a standardized
technique; excess heat will distort bacterial morphology
Heat fixation
a standardized
technique; the preferred method
Methanol fixation
are often identified using the acid
fast stain
Mycobacterium spp
With respect to O2, bacterial isolates can be classified as
– Obligate aerobes
– Microaerophilic aerobes
– Facultative anaerobes
– Aerotolerant anaerobes
– Obligate anaerobe
is the red dye that is driven through the bacterial cell wall using heat
Carbol fuchsin
Curved and spiral-shaped bacteria example
*Vibrio spp.
*Campylobacter spp.
*Helicobacter spp.
Examples of spiral-shaped bacteria
*Treponema spp.
*Borrelia spp
are bacteria, but they do not possess all the attributes of
typical bacterial cells.
Rickettsias, chlamydias, and mycoplasmas
– They are the smallest of the cellular microbes.
– They lack a cell wall and therefore assume many shapes
(i.e., pleomorphic).
– cause primary atypical pneumonia and genitourinary infections.
– Because they have no cell wall, they are resistant to drugs
like penicillin that attack cell walls.
– They produce tiny “fried egg” colonies on artificial media
Mycoplasmas
were discovered in
1977; they are prokaryotic organisms.
Archaea (meaning “ancient”)
Organisms with especially demanding nutritional
requirements are said to be
fastidious (“fussy”)
Examples of some common pathogenic bacteria
Neisseria meningitidis,
Salmonella typhi,
Shigella spp.,
Vibrio cholerae,
Yersina pestis,
and Treponema pallidum
Photosynthesis that does not produce oxygen is called
anoxygenic photosynthesis
