Cellular differentiation

single cell and multicellular differentiation along with morphogenesis of gram positive and gram negative bacteria

1. SUBMITTED BY: SANAM TULJA RAM/16-76 MORPHOGENESIS AND CELLULAR DIFFERENTIATION OF BACTERIAL CELL

2. Contents CELLULAR DIFFERENTIATION Definition Single cell differentiation Multicellular differentiation MORPHOGENESIS Definition Classification Gram positive bacteria Gram negative bacteria CASE STUDY

3. Cellular differentiation C ellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation is a process by which cell changes its functional and structural patterns under variable growth factors. Differentiation is an irreversible process.

4. Cell differentiation A) Single cell differentiation B)Multicellular differentiation Dimorphic life cycle Endospore formation Actinomycetes spores Cysts in azotobacter Heterocyst in cyanobacteria Fruiting body in myxobacteria Hyper flagellated swarmer cells

5. Single cell differentiation

6. Caulobacter crescentus is the best studied of the so called stalked bacteria. Caulobacter crescentus does not differentiate in response to nutritional stress or environmental cues but differentiation is a central part of the growth cycle. Two different cells are formed: - swarmer cells : motile and incapable of replicating its DNA. - stalked cells : nonmotile but capable of DNA replication.

7. Swamer cell: motility and dispersal Stalked cell : attached to some surface via its stalk/holdfast structure and gives off daughter swarmer cells. the swarmer cell shed its flagellum and pili.a stalk is produced at the same pole while DNA replication is initiated.

8. It is an extreme survival strategy employed by certain low G+C gram positive bacteria. The primary function of endospore formation appears to be the survival and dissemination of the species. When the environment becomes more favourable, the endospore can reactivate itself to the vegetative state. Time and effort has been expended in the study of this process in the genus Bacillus, particularly Bacillus subtilis .

9. Actively growing cells of B.subtilis are induced to differentiate into spores by starvation for carbon, nitrogen or in some cases phosphorous source (piggot 2004) Sporulation is an energy consuming process. It cannot proceed in complete absence of nutrients.

10. Under poor nutrition filamentous differentiate into spores. In contrast to endospores, these structures are part of reproductive process. Actinomycetes spores are capable of surviving for long periods of time(for years)

11. It involves simple formation of cross walls that divide filament into sections, each containing a chromosome. These then differentiate into mature spores. During this process a tougher cell wall is laid down and there is a conversion of cytoplasm to a dormant state.

12. Bacteria of genus azotobacter are nitrogen fixing, gram negative organotrophs. At the end of exponential growth, some cells undergo a final division and initiate the formation of cysts. A.vinelandii has been the object of intensive research on its growth, differentiation and genetic properties.

13. When the organism experiences a lack of nutrients, it will develop into cysts. The cell is then protected against desiccation by a multilayered coat of which gel-forming alginate is a necessary part. Depending on the carbon source and conditions, poly-b- hydroxybutyrate ( PHB) accumulates in vegetative cells.

14. In the presence of a source of combined nitrogen such as nitrate or ammonium,Anabena grows as a long filaments containing hundreds of photosynthetic vegetative cells. In the absence of combined nitrogen, it produces heterocysts at every ten to twenty vegetative cells along filaments.

15. Many cyanobacterial species are capable of nitrogen fixation. However, oxygenic photosynthesis and nitrogen fixation are incompatible processes because nitrogenase is in activated by oxygen.

16. Multicellular differentiation

17. Myxobacteria are a group of gram negative bacteria that are predominantly found in soil. During starvation, growth is arrested and a developmental program is initiated, which culminates in the formation of spore bearing fruiting bodies that have a well defined shape.

18. Within 4-6hrs after resources exhaustion fruiting body formation is evident. This is accompanied by changes in cell motility and the formation of aggregation centres. Within 24hrs, the aggregation process is complete, and the nascent fruiting bodies each containing approx 10^5 densely packed cells that differentiate into spores.

19. Myxococcus xanthus life cycle

20. Swarming is the fastest known bacterial mode of surface translocation and enables the rapid colonization of a nutrient rich environment and host tissues. It requires functional flagella and is coupled to the production of a viscous slime layer. Nutrient availability is crucial to sustain the energy demanding process of swarming.

21. P.mirabilis, in which elongated, multinucleated and hyper flagellated swarmer cells can spread as multinucleated rafts across surfaces. P.mirabilis flagellum functions as a mechanosensor of the surface signal. Both lipopolysaccharide(LPS) and O-antigen play a part in P.mirabilis surface sensing.

22. Species such as Proteus mirabilis and Vibrio parahaemolyticus , B.subtilis which are capable of vigorous swarming on high agar medium

23. Morphogenesis Morphogenesis  -from the Greek  morphê=  shape Genesis=  creation It is the biological process that causes an organism to develop its shape. The process controls the organized spatial distribution of cells during the embryonic development of an  organism. Morphogenesis can take place also in a mature organism. Morphogenesis also describes the development of unicellular life forms that do not have an embryonic stage in their life cycle, or describes the evolution of a body structure within a taxonomic group.

24. Reason for morphogenesis Morphogenetic responses may be induced in organisms by hormones, by environmental chemicals ranging from substances produced by other organisms to toxic chemicals as pollutants, and other plants, or by mechanical stresses induced by spatial patterning of the cells . Morphological differentiation is closely associated with fundamental growth and cell cycle process.

25. Morphological differentiation of bacteria Gram + ve bacteria Gram - ve bacteria High G+C Content Low G+C Content Actinomycetes Actinoplanes Streptomyces Nocardia Mycobacterium Corynebacterium Brevibacterium Bifidobacterium 1)Clostridia - clostridium Epulopiscium Sarcina Desulfotomaculum 2) Mollicutes 3)Bacilli 1) Anoxygenic photosynthetic bacteria 2)Oxygenic photosynthetic bacteria 3) Methylotrophic bacteria 4) Cyanomorphic bacteria 5)Stalked, swarmer and prosthecate bacteria

26. GRAM POSITIVE BACTERIA

27. The Mollicutes : The most important character of the Mollicutes is that their cells are not surrounded by a cell wall  These bacteria are unable to synthesise the precursors of peptidoglycans, the main component of bacterial wall. Due to the absence of a rigid wall, mollicutes are highly plastic and pleomorphic.

28. Class : Clostridia: ( a) Clostridium:  Clostridia are obligate anaerobes, endospore -forming and rod-shaped. Most species are motile with peritrichous flagella. Some Clostridia produce capsules, e.g. C. pectinovorans and C. perfringens . (b) Epulopiscium: An interesting organism, a giant bacterium, named Epulopiscium fishelsoni , isolated from the intestinal tract of brown surgeon fish. It is a motile, cigar-shaped enormously large organism. It is nearly a million times larger in volume than an average E. coli cell. c) Sarcina: Sarcina includes large cocci (up to 4 µm) in cell packets containing up to 64 cells held together by cellulose . (d) Desulfotomaculum : Anaerobic , rod-shaped, endospore -forming is peritrichously flagellate motile bacteria. Although the cell wall is of Gram-positive type, the bacteria stain as Gram-negative.

29. Class ‘Bacilli’: The genera include rods, cocci , mycelial forms and trichome -forming types. Endospores may or may not be present. They may be motile or non-motile; when motile they are usually peritrichously flagellate. 

30. GRAM NEGATIVE BACTERIA

31. Anoxygenic photosynthetic bacteria

32. Anoxygenic photosynthetic bacteria

33. Oxygenic photosynthetic bacteria

34. Oxygenic photosynthetic bacteria

35. Methylotrophic bacteria- proteobacteria

36. Cyanomorphic bacteria

37. Stalked bacteria

38. Prosthecate bacteria

39. Swarmer bacteria

40. Prosthecate and swarmer cells

41. Case study Received 23 July 2010 ; revised 15 March 2011 ; accepted 1 April 2011.

42. INTRODUCTON Proteus species, Gram-negative bacteria in the family Enterobacteriaceae Differentiation into swarmer cells, which are characterized by a 10 to 40-fold increase in cell length, a drastic increase in the number of flagella .

43. MATERIALS AND METHODS Proteus mirabilis strain L1N2 was grown in Trypto-soy broth or agar . Trypto-soy broth was adjusted to pH 5.0, 7.0 or 9.0, supplemented with 25g/L urea(designatedUT5,UT7orUT9,respectively) or without urea (T5, T7 or T9, respectively ) 1:10000 bacterial cells into 1mL broth at pH 5.0, 7.0 or 9.0, and incubating them at 37◦C for 12hr . Bacterial cells were harvested from the bacterial suspension by centrifugation at 12,000×g for 1min

44. Bacterial cells collected by centrifugation were resuspended to a concentration of 10 mL in PBS containing 2 μ g/mL of DAPI ( 4,6-diamidino-2-phenylindole) The bacterial cells were examined with an Eclipse TE2000-U fluorescence microscope for estimation of cell length. Bacterial flagella were observed with an H-800 transmission electron microscope.

45. Results Bacterial cells longer than 10 μ m were defined as swarmer morphotypes. The final pH values of broth media T5, T7, T9, UT5, UT7 and UT9 were 4.9, 6.0, 8.0, 8.7, 9.2 and 9.2, respectively . pH values percentage of swarmer morphotypes T5 0.6% T7 0.2% T9 less than 0.1% UT5 1.8% UT7 1.8% UT9 0.1%

46. Swarmer morphotypes appeared in acidic rather than alkaline broth, irrespective of the addition of urea. Elongated and multinucleated cells grown in broth media, which were morphologically similar to swarmer cells grown on agar plates, were stained with DAPI. More than 70% of the P. mirabilis L1N2 cells on agar plates were longer than 10μm

47. Electron microscopic photos of bacterial cells grown in each broth are shown in Figure2. Elongated and hyperflagellated cells, as well as short swimmer cells expressing many flagella, were evident in UT5 . Similarly, bacterial cells grown in T7, T9 and UT7 also expressed peritrichous flagella . The number of flagella on bacterial cells grown in T5 and UT9 was markedly decreased.

48. Conclusion Results suggest that P. mirabilis cells differentiate into swarmer morphotypes at an early phase of infection when the host’s urine is acidic, but they dedifferentiate into swimmer morphotypes when the urinary pH is increased . In conclusion, 1.8% cells of P. mirabilis L1N2 differentiated into hyperflagellated and multinucleated swarmer morphotypes in acidic broth containing urea. On the other hand, P . mirabilis grown in alkaline broth containing urea showed few elongated cells, and low levels of flagella production

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