xid-133556_1 - Today’s factoid[in Biology in the News...

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Unformatted text preview: Today’s factoid [in Biology in the News folder on BB] • new research is Fnding that a few resistant bacterial cells can help an en;re bacterial popula;on survive exposure to an;bio;cs • a cri;cal problem for human infec;ous diseases caused by bacteria • "supermutant" cells are altruis(c ¡ they help other cells survive at a cost to themselves (slower growth) • in addi;on to producing gene products directly associated with resistance, "supermutant" cells also produce indole compounds that signal to the other cells and generally help cells survive harsh environments (probably by triggering stress responses) • i.e. bacteria are ac;ng as a popula;on or possibly even a community (if mul;ple species are involved), not all as selFsh individual cells, as previously thought http://www.nsf.gov/news/news_summ.jsp? cntn_id=117596&WT.mc_id=USNSF_51&WT.mc_ev=click http://www.topnews.in/healthcare/general/health-news?page=5 When did Prokaryotes originate? >2 bya >3 bya • First fossils – 3.5 billion years ago (bya) • First fossil evidence of cellular life – But there was already signi¡cant diversity • Billions of years to adapt and diversify before Eukaryotes appeared Many prokaryotes cannot be cultured Only about 5000 species described Actual number possibly in the When did Prokaryotes originate? >2 bya >3 bya • First fossils – 3.5 billion years ago (bya) • First fossil evidence of cellular life – But there was already signi¡cant diversity • Billions of years to adapt and diversify before Eukaryotes appeared Many prokaryotes cannot be cultured Only about 5000 species described Actual number possibly in the millions Prokaryote success • Es;mated 3x10 28 bacteria and archaea cells in the ocean • There are more bacteria in a single human intes;nal tract than all the humans who have ever existed • Found in just about all imaginable environments – Many extreme environments • Most are unicellular (but some mul;cellular forms known) • Large diversity, but three most common forms are: cocci , bacilli (rods) , and helices Cell wall diversity in Prokaryotes • Chemically very diferent From plant, algae, and Fungal cell walls • A major method oF classiFying bacteria : Gram staining ‐ [purple dye Followed by iodine, then alcohol wash and a red counterstain] An;bio;cs like penicillin and ampicillin interFere with pep;oglycan synthesis Bacterial cell well components are good targets For an;bio;cs. (why?) Some other Prokaryote features: movement • Some species use flagella (structurally diFerent from Eukaryote flagella) • Other species – Axial ¡laments • Spiral movement – Gas vesicles • Up and down in water column a spirochaete a cyanobacterium Salmonella Some other Prokaryote features: sex • Reproduc;on is asexual – Binary Fssion hAp://www.textbookoCacteriology.net/growth.html • But many species can undergo gene;c recombina;on – e.g. E. coli bacteria use a conjuga;on system...
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xid-133556_1 - Today’s factoid[in Biology in the News...

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