Ordinary Gram-Positive Bacteria

The world of Bacteria II Ordinary Gram Positive Bacteria.

1. The world of Bacteria II: “Ordinary” Gram-Positive Bacteria Anil Shrestha Msc Medical Microbiology

2. 1) Aerobic/ Facultatively Anaerobic Cocci They possess cytochrome. They are able to respire with oxygen, i.e., have an oxidative type of metabolism. Some can also obtain energy under anaerobic conditions by fermentation (have a fermentative type of metabolism). Deinococcaceae and Micrococcaceae is the family for this organism.

3. DEINOCOCCACEAE The cocci occur mainly in tetrads or cubical packets. The organisms have an unusually high resistance high resistance to gamma and ultraviolet radiation. Eg : Deinococcus radiodurans

4. MICROCOCCACEAE The cocci occur mainly in clusters, tetrads, or cubical packets of eight cells. The cells donot exhibit any unusal resistance to gamma and ultraviolet radiation. The genera included are Micrococcus:- 1) nonmotile , aerobic, oxidative, catalase positive. Planococcus :- 1) motile, aerobic, oxidative, catalase positive. Staphylococcus:- nonmotile , facultative anaerobes, fermentative, catalase positive.

5. 2) Aerotolerant fermentative cocci They do not possess cytochromes. They have only a fermentative type of metabolism and do not respire; yet they can grow anaerobically or aerobically. The cells are arranged in pairs, chains, or tetrads. Streptococcus:- arranged in pair or chains, catalase negative, homofermentative.i.e , the predominant end product of sugar fermentation is lactic acid.

6. Lancefield grouping is a method of grouping catalase -negative, coagulase -negative bacteria based on the carbohydrate composition of bacterial antigens found on their cell walls. Classification Group A - Streptococcus pyogenes Group B - Streptococcus agalactiae Group C - Streptococcus equisimilis , Streptococcus equi , Streptococcus zooepidemicus , Streptococcus dysgalactiae Group D - Enterococci , Streptococcus bovis Group E - Streptococcus milleri and mutans Group F - Streptococcus anginosus Group G - Streptococcus canis and Streptococcus dysgalactiae Group H - Streptococcus sanguinis Group L - Streptococcus dysgalactiae Group M - Streptococcus fryi sp. nov Group N - Lactococcus lactis Group R&S - Streptococcus suis other Streptococcus species are classified as 'non-Lancefield Streptococci'

7. Though there are many groups of streptococcus, only five are known to commonly cause disease in immune-competent human beings: Group A, Group B, both members of Group D, and two groups that lack the Lancefield carbohydrate antigen: Streptococcus pneumoniae and Viridans streptococci .

8. Leuconostoc :- C occi are arranged in pairs and chains. Catalase negative Heterofermentative ; produce CO₂ and ethanol or acetic acid in addition to lactic acid. Pediococcus :- Cocci occur in pairs and tetrads. Catalase negative. Exhibit homolactic type of fermentation. Pediococci are saprophytes and are particularly noted for their ability to form capsular material that causes beer to become ropy and viscous.

9. 3) Anaerobic Gram Positive Cocci These cocci have a fermentative type of metabolism. Some genera must be supplied with a fermentable carbohydrate in order to grow; others can ferment amino acids and do not require carbohydrates. Lactic acid is not a major fermentation product. Most genera form CO₂, H₂, short-chain fatty acids, and in some cases ethanol or succinic acid.

10. Genus Arrangement of Cells Main Sources of Carbon and Energy Occurrence Peptococcus Pairs, clusters, tetrads, and short or long chains Peptone or amino acids Human intestine and respiratory tract; clinical specimens Peptostreptococcus Pairs and short or long chains Peptone or amino acids Human clinical specimens Ruminococcus Pairs and short or long chains Carbohydrates Bovine and Ovine rumen Coprococcus Pairs and short or long chains Carbohydrates Human feces Sarcina Cubical packets of eight cells Carbohydrates Soil; mud; cereal grains; diseased human stomachs

11. Endospore-forming Gram-Positive bacteria

12. Aerobic/ Facultatively Anaerobic Sporeforming Rods and Cocci Bacillus Rod-shaped bacteria. Most species are harmless saprophytes occurring in soil, freshwater, or sea water. Many form exocellular enzymes that hydrolyze proteins or complex polysaccharides, activities that are often important causes of food spoilage. Because of the heat resistance of endospores, Bacillus species may species may survive milk pasteurization or inadequate heat treatment during canning of foods. Eg :- B. stearothermophilus , B. polymyxa , B. thuringiensis , B. anthracis

13. Sporosarcina Cocci arranged in tetrads or cubical packets of eight cells Widely distributed in fertile soil, where they play an active role in the decomposition of urea.

14. Anaerobic spore-forming Rods Clostridium :- have fermentative type of metabolism C. botulism C. tetani C. perfringens C. thermosaccharolyticum

15. Desulfotomaculum Obtain energy by anaerobic respiration, with sulfate serving as the terminal electron acceptor and organic substrates such as lactic or pyruvic acid serving as electron donor. Large amounts of H₂S are formed during growth.

16. Non spore forming Gram-Positive rods of Regular shape Genus Morphology and Motility Oxygen Relationship Catalase test Lactobacillus Long to very short rods, often in chain; usually motile Strictly fermentative organism, but can usually tolerate air; some strains are anaerobic Negative Listeria Very short rods, often in chains; motile by peritrichous flagella Aerobic to microaerophilic Positive Erysipelothrix Filament-forming rods; nonmotile Aerobic Negative

17. Non sporeforming Gram-positive rods of irregular shape

18. Aerobic/ Facultatively anaerobic nonfilamentous rods Straight to slightly curved rods that exhibit swellings, club shapes, or other deviations from a uniform rod shape. An aerobic or facultatively anaerobic nature, being capable of a respiratory type of metabolism and in some instances also of a fermentative type of metabolism. Eg :- Corynebacterium

19. Anerobic nonfilamentous or filamentous rods Actinomyces ( Facultative anaerobes) propionibacterium

20. Mycobacterium Nocardia