Unit IV.B The Prokaryotes (The Gram-Positive Bacteria) Flashcards
- include common soil bacteria, the lactic acid bacteria, and several human pathogens.
*important endospore-forming bacteria such as the genera Clostridium and Bacillus. Also of extreme importance in medical microbiology are the genera Staphylococcus, Enterococcus, and Streptococcus.
Low G + C gram-positive bacteria (Firmicutes)
- include mycobacteria, corynebacteria, and actinomycetes.
- related to gram-positive bacteria because they share common rRNA sequences.
High G + C gram-positive bacteria (Tenericutes)
obligate anaerobes; rod-shaped cells contain endospores that usually distend the cell
C. tetani: tetanus
C. botulinum : botulism
Clostridium
Clostridiales
- cigar shaped with 80 mm:600 mm in length, can be seen with the unaided eye
- Epulopiscium fishelsoni doesn’t reproduce by binary fission, daughter cells formed within the cell are released through a slit opening in the parent cell.
Epulopiscium
Clostridiales
- typically rods that produce endospores, common in soil, and only a few are pathogenic to humans
- Several species produce antibiotics.
(Bacillus anthracis causes anthrax, a disease of cattle, sheep, and horses that can be transmitted to humans )
Bacillus
Bacillales
occur in grapelike clusters
Staphylococcus aureus yellow-pigmented colonies (aureus = golden), facultative anaerobes,can grow in high osmotic pressure and low moisture
Staphylococcus
Bacillales
lactic acid–producing bacteria aerotolerant and capable of growth in the presence of oxygen
Lactobacillus
Lactobacillales
- spherical, gram-positive bacteria that typically appear in chains
- Pathogenic streptococci produce several extracellular substances that contribute to their pathogenicity.
Streptococcus
- adapted to areas of the body that are** rich in nutrients but low in oxygen** → gastrointestinal tract, vagina, and oral cavity.
- found in large numbers in human stool
- persist as contaminants in a hospital environment, on hands, bedding, and even as a fecal aerosol, high resistance to most antibiotics
Enterococcus:
Listeria monocytogenes can contaminate food, especially dairy products.
survives within phagocytic cells and is capable of growth at refrigeration temperatures
If it infects a pregnant woman, the organism poses the threat of stillbirth or serious damage to the fetus.
Listeria
highly pleomorphic because they lack a cell wall
* smallest self-replicating organisms, ranging from 0.1 to 0.25 μm
Mycoplasma
highly pleomorphic in their morphology
Actinobacter (High G + C Gram-Positive Bacteria
aerobic, non–endospore forming rods
myco (funguslike) → exhibition of filamentous growth
Mycobacterium
2 groups of Mycobacterium:
- slow growers
- fast or rapid growers
- coryne (club-shaped), tend to be pleomorphic, and their morphology often varies with the age of the cells
- C. diphtheriae the causative agent of diphtheria
Corynebacterium
Ability to form propionic acid; some species are important in the fermentation of Swiss cheese.
* P. acnes are bacteria that are commonly found on human skin and are implicated as the primary bacterial cause of acne.
Propionibacterium
- Gardnerella vaginalis is a bacterium that causes one of the most common forms of vaginitis.
- There has always been some difficulty in assigning a taxonomic position in this species, which is gram variable and exhibits a highly pleomorphic morphology.
Gardnerella
causes nitrogen-fixing nodules to form in alder tree roots, much as rhizobia cause nodules on the roots of legumes.
Frankia
Actinomycetes
- best known of the actinomycetes and most commonly isolated from soil
- produce a gaseous compound called geosmin, which gives fresh soil its typical musty odor
- produce most of our commercial antibiotics
Streptomyces
actinomycetes
- facultative anaerobes that are found in the mouth and throat of humans and animals.
- form filaments called hyphae that can fragment
- A. israelii causes actinomycosis, a tissue destroying disease usually affecting the head, neck, or lungs.
actinomyces
aerobic and common in soil
* to reproduce, they form rudimentary filaments, which fragment into short rods.
* N. asteroides, cause a chronic, difficult-to-treat pulmonary infection.
Nocardia
thrive in salt concentrations of more than 25%, → Great Salt Lake and solar evaporating ponds.
halophiles
optimal growth temperature is 80°C or higher.
thermophilic archaea
can be found growing at pH values below zero and frequently at elevated temperatures, as well.
Acidophilic archaea
oxidize ammonia for energy.
nitrifying archaea
strictly anaerobic archaea that produce methane as an end-product by combining hydrogen (H2) with carbon dioxide (CO2).
Methanogens