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