Acellular and Prokaryotic Microbes

• microbes


  can be divided into those that are truly cellular and those that are acellular
• Cellular microbes


  can be divided into those that are prokaryotic and those that are eukaryotic
• acellular microbes


  Viruses, viroids, and prions are often referred to as
• Virions

  Complete virus particles
• 10 to 300 nm in diameter.


  range of most viruses
• virus


  infect humans, animals, plants, fungi, protozoa, algae, and bacterial cells
• oncogenic viruses/oncoviruses


  viruses that cause specific types of cancer
• capsomeres


  a capsid comprise these protein units
• capsid


  a typical virion consists of a genome of either DNA or RNA, surrounded by this protein coat
• enveloped viruses


  viruses that have an outer envelope composed of lipids and polysaccharides
• Animal Viruses


  escape from their host cells either by lysis of the cell or by budding
• Attachment, Penetration, Uncoating, Biosynthesis, Assembly


  Steps in the multiplication of animal viruses
• enveloped viruses


  Viruses that escape by budding become
• Latent Virus Infections


  Viral infections in which the virus is able to hide from a host’s immune system by entering cells and remaining dormant
• Human immunodeficiency virus


  This virus causes acquired immunodeficiency syndrome
• Human immunodeficiency virus 


  It is an enveloped, single-stranded RNA virus
• CD4+ cells


  The primary targets for HIV —those having CD4 receptors on their surface
• Antiviral agents


  drugs that are used to treat viral infections
• antiviral agents


  These agents interfere with virus-specific enzymes and virus production by disrupting critical phases in viral multiplication or inhibiting synthesis of viral DNA, RNA, or proteins
• bacteriophages


  Viruses that infect bacteria
• virulent bacteriophages and temperate bacteriophages


  two categories of bacteriophages
• Virulent bacteriophages

  always cause what is known as the lytic cycle, which ends with the destruction of the bacterial cell
• attachment, penetration, biosynthesis, assembly, and release


  five steps in the lytic cycle
• viroids and prions


  smaller and less complex infectious particles than viruses
• viroids


  short, naked fragments of singlestranded RNA, which can interfere with the metabolism of plant cells
• viroids


  transmitted between plants in the same manner as viruses
• prions


  small infectious proteins that cause fatal neurologic diseases in animals and humans called transmissible spongiform encephalopathies
• transmissible spongiform encephalopathies


  prions cause small infectious proteins that cause fatal neurologic diseases in animals and humans called
• prions


  are the most resistant to disinfectants of all pathogens
• Gram-negative, Gram-positive, and those that lack a cell wall


  three major phenotypic categories of bacteria
• cocci, bacilli, curved and spiral-shaped


  three basic categories of bacteria based on shape
• 1 µm in diameter

  average coccus
• cocci

  round shape bacteria
• bacilli


  often referred to as rods; they may be short or long, thick or thin, and pointed or with curved or blunt ends
• 1 x 3 µm


  average sized bacillus
• coccobacilli

  extremely short bacilli
• Borrelia hermsii


  cause of relapsing fever
• fixation


  serves to kill organisms, preserve their morphology, and anchor the smear to the slide
• heat fixation


  not a standardized technique as excess heat will distort bacterial morphology
• methanol fixation


  a standardized technique and the preferred method