H nana
Friday, September 19, 2008
H nana
Egg of H nana showing hooklets and polar filaments
It is colorless, oval or round, 30-45 µm in diameter
Hooklets are present in the embryo. Careful focusing reveals 3 pairs of hooklets.
At each end of the egg, thread like structures called polar filaments is usually visible
Draughtsmen colony
The colonies of Streptococcus pneumoniae are raised in young but as the culture ages, the they become flattened, with a depressed central part and raised edges giving them a ringed appearance (Draughtsmen colony).
Streptococcus pneumoniae is catalase-negative and facultative anaerobic, but can grow aerobically. However, 8% of clinical pneumococcal isolates require an enriched carbon dioxide atmosphere if they are cultured on a solid medium, and thus it is recommended that cultures be incubated in a CO2 enriched atmosphere. In all cases, the nutritionally fastidious bacterial growth requires a source of catalase (blood or serum) to neutralize the large amount of hydrogen peroxide produced by the bacteria and they are unable to synthesize hemin. By the action of pyruvate oxidase (SpxB) under aerobic growth conditions, pneumococcus utilizes oxygen to form hydrogen peroxide. Hydrogen peroxide is toxic to epithelial cells and other bacteria such as H influenzae, S aureus etc. Hydrogen peroxide destroys the labile constituents of the pneumococcal cell and thus, pneumococcus may destroy itself if hydrogen peroxide is allowed to accumulate.
Streptococcus pneumoniae also contains within itself the enzymatic ability to disrupt and to disintegrate the cells (bacterial peptidoglycan). The enzyme is called an autolysin. The major pneumococcal autolysin, N-acetylmuramoyl-L-alanine amidase is also known as LytA amidase. The physiological role of this autolysin is to cause the culture to undergo a characteristic autolysis that kills the entire culture when grown to stationary phase. Virtually all clinical isolates of pneumococci harbor this autolysin and undergo lysis usually beginning between 18-24 hours after initiation of growth under optimal conditions. Autolysis is consistent with changes in colony morphology. Colonies initially appear with plateau-type morphology, then starts to collapse in the centers when autolysis begins.
The minimum criteria for identification and distinction of pneumococci from other streptococci are Gram positive staining, alpha hemolytic activity and bile or optochin sensitivity. Bile solubility test is based on the presence of an autolytic enzyme LytA. Lysis of pneumococcal cells by autolytic enzyme, LytA, is enhanced in the presence of bile salts like sodium deoxycholate
Streptococcus pneumoniae is catalase-negative and facultative anaerobic, but can grow aerobically. However, 8% of clinical pneumococcal isolates require an enriched carbon dioxide atmosphere if they are cultured on a solid medium, and thus it is recommended that cultures be incubated in a CO2 enriched atmosphere. In all cases, the nutritionally fastidious bacterial growth requires a source of catalase (blood or serum) to neutralize the large amount of hydrogen peroxide produced by the bacteria and they are unable to synthesize hemin. By the action of pyruvate oxidase (SpxB) under aerobic growth conditions, pneumococcus utilizes oxygen to form hydrogen peroxide. Hydrogen peroxide is toxic to epithelial cells and other bacteria such as H influenzae, S aureus etc. Hydrogen peroxide destroys the labile constituents of the pneumococcal cell and thus, pneumococcus may destroy itself if hydrogen peroxide is allowed to accumulate.
Streptococcus pneumoniae also contains within itself the enzymatic ability to disrupt and to disintegrate the cells (bacterial peptidoglycan). The enzyme is called an autolysin. The major pneumococcal autolysin, N-acetylmuramoyl-L-alanine amidase is also known as LytA amidase. The physiological role of this autolysin is to cause the culture to undergo a characteristic autolysis that kills the entire culture when grown to stationary phase. Virtually all clinical isolates of pneumococci harbor this autolysin and undergo lysis usually beginning between 18-24 hours after initiation of growth under optimal conditions. Autolysis is consistent with changes in colony morphology. Colonies initially appear with plateau-type morphology, then starts to collapse in the centers when autolysis begins.
The minimum criteria for identification and distinction of pneumococci from other streptococci are Gram positive staining, alpha hemolytic activity and bile or optochin sensitivity. Bile solubility test is based on the presence of an autolytic enzyme LytA. Lysis of pneumococcal cells by autolytic enzyme, LytA, is enhanced in the presence of bile salts like sodium deoxycholate
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