. The cytology and life-history of bacteria. Bacteria. LIFE-CYCLES IN BACTERIA 131. Fig. 58 LIFE-CYCLE OF AZOTOBACTER An extraordinary degree of complexity is found in the life-cycle of the nitrogen-fixing bacterium Azotobacter. Not only does this organism produce spore-like cysts (not illustrated here), but two distinctly different types of gonidia. The vegetativ'e cell [A] becomes packed with tiny replicas of itself (C), or with motile gonidia (G, H). In both cases, the cycle is initiated by the production, within the mother-cell of an undifferentiated mass of Gram-positive material [B] ; tr
. The cytology and life-history of bacteria. Bacteria. LIFE-CYCLES IN BACTERIA 131. Fig. 58 LIFE-CYCLE OF AZOTOBACTER An extraordinary degree of complexity is found in the life-cycle of the nitrogen-fixing bacterium Azotobacter. Not only does this organism produce spore-like cysts (not illustrated here), but two distinctly different types of gonidia. The vegetativ'e cell [A] becomes packed with tiny replicas of itself (C), or with motile gonidia (G, H). In both cases, the cycle is initiated by the production, within the mother-cell of an undifferentiated mass of Gram-positive material [B] ; traces of Gram-positivity may be retained to a later stage of gonidium production. The large gonidia (C, D, E) grow up directly into typical vegetative cells, and are retained within the remains of the mother-cell wall. The small, motile gonidia (G, H, I) may reproduce for several generations as small. Gram-negative bacteria. Fig. 57 BACTERIAL GONIDIA Bacterial gonidia are also well seen in A:otobactey, which produces more than one kind, and in some spiral organisms. (1) Azotobacter mother cells showing large and small gonidia (compare Fig. 58). The large types grow directly into vegetative cells, the small gonidia may reproduce as such for several generations. (Gram's stain, x 3000). (2) Small gonidium of Azotobacter. It resembles those of Rhizobium but has more fiagella and is less nearly spherical. (Electron micrograph, gold-shadowed, X 16,000). (3) Electron micrograph of Spirilliiin sp. showing attached cysts, from which the gonidia are produced. ( â 6000). (4) ^Mature cyst with fiagella still attached. ( â 12,000). (5) Developing gonidia, of Spirillum, each with a single polar flagellum. Note the liU^pharoplasts. ( â 12,000).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bisset, Kenneth Alexander. B
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectbacteria
