Shapes of Eubacteria Yourtasks Copythediagramshowingthedifferentshapes of Eubacteria Identifytheshape of the bacteria in thepicturesbelow Drawhowyouwouldexpectthe bacteria to look fromthegivennames of the bacteria below. Label my shape! Draw me! Streptoccocusbovis Staphylococcusaureus Didyouknow! Bacterria can alter theirshape as a result of ageingorenvironmental shock! Thisisknown as pleomorphy. a) b) c)
Positions of flagellum Polar attachment Flagellumattached at oneorbothends Peritrichiousattachment Flagelladispersedrandomlyoverthesurface of thebacterium Task: Make a note of the different types of flagellum attachment Use your knowledge to identify the type of flagellum attachment in the pictures to the left View slide
Presence of fimbrae Task: Use thewords in thewordbankbelowtocopyouttheparagraph and fill in theblanks! __________ are short and rigid bristle-like projections that are anchored in the bacterial __________ membrane. They stretch out past the bacterial cell __________Fimbriae act as __________(marker molecules) and can also interact with the __________ cell membrane. In__________ (disease-causing) bacteria, the presence of a large number of fimbriae may help to prevent __________by the host cells. WORD BANK wall fimbriae phagocytosis plasma antigens pathogenic host View slide
Endospores Task: Writeoutthesentencesbelow in thecorrectorderto describe endosporeformation. When the environmental conditions are suitable, the endospore absorbs water, swells and the wall splits, releasing the cell inside. During this process, a portion of the cytoplasm and a copy of the bacterial chromosome undergo dehydration The resulting structure, called endospore can tolerate extreme environmental conditions and can remain viable for several years. The dehydrated organelles then get surrounded by a three-layered covering. It develops a new cell wall and starts functioning as a typical bacterial cell again. In certain bacteria like Clostridium and Bacillus, the cells tide over unfavourable conditions by forming endospores. Finally, the remaining part of cytoplasm and cell wall degenerate.
Bacterial Capsule Function
considered a virulence factor
enhances the ability of bacteria to cause disease (i.e. prevents phagocytosis)
capsule is slippery and fragile, so when a phagocyte tries to phagocytose the bacteria, it can slip away
capsules also contain water which protects bacteria against dessication
exclude bacterial viruses and most toxic materials such as detergents
capsules also help cells adhere to surfaces.
Tasks: Make notes onthevariousaspects of bacterial capsules Usethedictionarytofinddefintionsforthewords in red Composition
usually composed of polysaccharides
Location and size very large structure lies outside the bacterial cell wall not easily washed off the cause of various diseases
Vibriofischeri Tasks Readthearticletakenfrom a scientific magazine below. Answerthequestionsbasedonthearticle in FULL, MEANINGFUL sentences The marine bacterium V. fischeri exists naturally either in a free-living planktonic state or as a symbiont of certain luminescent fish or squid (Ruby & Nealson, 1976, Ruby & McFall-Ngai, 1999). The bacteria colonisespecialised light organs in the fish or squid, which cause them to bioluminesce. Luminescence in the fish or squid is thought to be involved in the attraction of prey or even as camouflage. During the nocturnal feeding of the squid Euprymnascolopes, luminescence from the light organ is directed towards the sea floor and is modulated by the squid to match the intensity of moonlight, therefore preventing a shadow of the squid on the sea floor (Visick & McFall-Ngai, 2000). The source of the luminescence is the bacteria themselves. In the marine environment, the bacteria only luminesce when colonising the light organs and do not emit light when in the free-living state. It makes good evolutionary sense for the bacteria to tightly regulate bioluminescence as the mechanism by which light is produced is very energy intensive. Research carried out to answer the question of how V. fischeri regulates bioluminescence led to the discovery of bacterial quorum sensing. In which habitat is V. fischerinormally found? The bacterium is described as a ‘symbiont’. What does that mean? Which parts of the squid do V. fischericolonise? Define ‘bioluminescence’ How does the squid use bioluminescence in order to escape predators? Why does V. fischeritightly regulate bioluminescence?
Quorum Sensing Tasks: Copythediagramtotheright Annotateyourdiagramwiththeadditional notes below Bioluminescence Quorum sensing the regulation of a bacterial process that depends on the density of the bacterial population Bacteria produce signalling molecules known as autoinducers These signalling molecules are detected by special receptors in the bacterial cell membrane When the bacterial population is low then the diffusion of autoinducer into the surroundings is almost zero As the population size increases the concentration of autoinducer reaches a threshold causing gene expression The genes are expressed because the binding of the autoinducer to the receptor causes the bacteria to start making moreautoinducer and other specific enzymes
Biofilms Watch the video on ‘Understanding Biofilms’ Task: Make notes thatexplain -what a biofilmis -how a biofilmforms -whatdoes a biofilm look like Handy Hint! Youwon´tneedtowatchthewhole video You CAN rewind and fast forward it!