Bacterial morphology gliding and fruiting bacteria

Gliding and fruiting bacteria
1st Sem MSc

1. Bacterial morphology

2. Gliding and fruiting bacteria The organisms of this group are Gram-negative, nonphototrophic , and nonflagellated . They exibit a creeping or gliding motility on solid surfaces. It is independent of propulsive structures such as flagella, pili, and fimbriae. Gliding allows microorganisms to travel along the surface . The exact mechanism of gliding is not known . The mechanisms responsible for bacterial gliding motility have been a mystery for almost 200 years. The mechanisms of movement employed by these bacteria are still a matter of speculation . Genetic, biochemical, ultrastructural, and behavioral studies are providing insight into the machineries employed by these diverse bacteria that enable them to glide over surfaces. KKR1116 2

3. . When the organisms are placed on a solid culture medium,growth , which is frequently of a slimy consistency, spreads rapidly over the surface. As the cells glide across the surface of the medium, they leave a layer of slime behind them. Indeed, the prefix myxo , which occurs in the name of the order to which these bacteria belong, Myxobacterales , reflects this property,being derived from the Greek noun myxo , meaning “mucus, slime” . Although there are some exceptions, a remarkable and striking feature of the myxobacters is that the vegetative cells at some stage of growth, swarm together in masses and form fruiting bodies [This behavior bears some resemblance to that of slime molds. KKR1116 3

4. Myxobacterial gliding motility. KKR1116 4

5. The fruiting bodies contain myxospores , which are shorter and thicker than the vegetative cells and are resistant to desiccation and ultraviolet radiation but not to heat. The fruiting bodies range from simple to complex. The simplest fruiting bodies are merely heaps of myxospores embedded in a mass of slime. The most elaborate fruiting bodies may have a stalk composed of slime, and walled containers ( sporongioles , sometimes termed cysts) which enclose the myxospores . Myxobacters are strictly aerobic organisms found in surface layers of soil, compost, manure. rotting wood, and animal dung. Many myxobacters develop very colorful pigments in their normal environment. Some species produce exocellular enzymes that degrade complex substrates such as cellulose, agar, chitin, and even the cell walls of other bacteria. KKR1116 5

6. Stages in the fruiting body formation of the myxobacter Chondromyces crocotus . Early stages: (A) Initial stages of vegetative cell aggregation; (B) fried-egg stage showing orientation of peripheral cells; (C) bulb formation and development of stalk. Late stages: (U) Initial stages of sporangiole formation; (B) sporangiole formation after elongation of stalk to Maximum length. Structures range in size from approximately 10 to 60 p.m. (From P. L. Grilione and J. Pang born and J Bacterial KKR1116 6

7. Fruiting bodies of Myxobacteria . KKR1116 7

8. Sheathed bacteria Sheathed  bacteria  are bacteria that grow as long filaments whose exterior is covered by a layer known as a sheath. Bacteria in this group are Gram-negative, aerobic, and nonphototrophic . Within the sheath, the bacteria can be capable of growth and division. Examples of sheathed bacteria include   Leptothrix discophora   (also known as "iron bacteria"), and  Sphaerotilus natans . Sheathed bacteria are common of the bacterial communities in water and in soil. KKR1116 8

9. In these environments, the sheath is often coated with precipitates of elements in the water or soil environments, such as oxides of iron and manganese. The sheath that covers the bacteria can be of varied construction. Much of the structural information has been gleaned from the observation of thin slices of sample using the transmission  electron microscope  . KKR1116 9

10. Bacterial sheaths tend to be manufactured when the bacteria are in an aquatic or soil environment that contains high amounts of  organic matter . The sheath may serve to provide protection to the bacteria in these environments, Also, the ability of metallic compounds to precipitate on the sheath may provide the bacteria with a ready supply of such inorganic nutrients. Sheaths may also help the bacteria survive over a wide range of temperature and  pH  , by providing a relatively inert barrier to the external environment. The  Sphaerotilus - Leptothrix  group of organisms, also known informally and collectively as ‘sewage fungus’. KKR1116 10

11. Sphaerotilus natans KKR1116 11

12. Leptothrix discophora KKR1116 12

13. Actinomycetes Classification Kingdom:  Bacteria Phylum : Actinobacteria Subclass: Actinobacteridae Order : Actinomycetales Actinomycetes are unicellular, Gram-positive bacteria that belong to the Order Actinomycetales . Members of this group are widely distributed in nature and can be found in a variety of habitats across the world. They have been shown to share a number of characteristics with fungi . KKR1116 13

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16. Actinomycetes are best known for nitogen fixations in non-leguminous plants. KKR1116 16

17. Microscopic view of actinomycetes . KKR1116 17

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20. Reproduction Actinomycetales have 2 main forms of reproduction;  spore  formation and hyphae fragmentation. During reproduction, Actinomycetales can form  conidiophores , sporangiospores , and oidiospores . In reproducing through hyphae fragmentation, the hyphae formed by Actinomycetales can be a fifth to half the size of fungal hyphae, and bear long spore chains. KKR1116 20

21. Antimicrobial properties : Many species of Actinomycetes produce antimicrobial compounds under certain conditions and growth media.  Streptomycin ,  actinomycin , and streptothricin are all medically important antibiotics isolated from Actinomycetes bacteria. [1]  Almost two-thirds of the natural antimicrobial drug compounds used currently are produced by different species of Actinomycetes . [2] KKR1116 21

22. Refreneces Microbiology by Michael j.pelczar www.encyclopedia.com www.britannica.com www.wikipedia.com KKR1116 22