Bacterial Communica/on

Transcription

1 Bacterial Communica/on Professor Amy Camp Department of Biological Sciences Bioscience in the 21 st Century October 26, 2011

2 Outline I. Microbiology overview II. Bacterial communicagon Quorum sensing Cell cell communicagon during Bacillus sub*lis sporulagon 2

3 Outline I. Microbiology overview II. Bacterial communicagon Quorum sensing Cell cell communicagon during Bacillus sub*lis sporulagon 3

4 Microbiology: The study of small (microscopic) organisms Bacteria Viruses* Pro*sts hop:// hop:// Fungi Archaea hop:// hop://web.mit.edu/ hop:// 4

5 It s a microbial world! (No really. It is.) 7,000,000,000 ~7 x 10 9 people 200,000,000,000 ~2 x burgers 15,000,000,000,000 ~1.5 x dollars 8,000,000,000,000,000,000 ~8 x grains of sand 10,000,000,000,000,000,000,000 ~1 x stars 1,000,000,000,000,000,000,000,000,000,000 ~1 x bacteria 10,000,000,000,000,000,000,000,000,000,000 ~1 x bacteriophage 5

6 Spore forming bacteria in a speck of soil 540 Spore-forming Bacteria!!! 6

7 Where can microbes be found? Everywhere, on every surface, all the Gme Water, soil, and air Deep in the earth High in the atmosphere In and on all plants and animals Human microbiome Human body = ~10 trillion human cells + ~100 trillion bacterial cells! 7

8 Benefits of the human microbiome 1. Aid in diges/on. Bacteria break down many of the complex carbohydrates we eat into products that can be absorbed by the body. We absorb 15 20% of our caloric intake in this way! 2. Compe//ve bacterial interac/ons. Good bacteria occupy niches that might otherwise be infected by pathogens. Example: Clostridium difficile infecgon following angbiogc treatment. 3. Immunomodula/on. Endogenous bacteria in our bodies are crigcal for proper development and training of our immune system. The Hygeine Hypothesis posits that the increased use of angmicrobial products resulgng in reduced exposure of children to bacteria and other microbes is responsible for the increased incidence of allergies and asthma and other related disorders. 8

9 Microbial colonies Microbes are almost always invisible but somegmes we can see them! Petri plate Acid mine drain (ph 0) Rainbow Pool Yellowstone NaGonal Park 9

10 Bioluminescent bacteria seen from space! Miller et al.,

11 Bioluminescent bacteria seen from space! Miller et al.,

12 Not only are microbes incredibly abundant, but they also consgtute the vast majority of Earth s biodiversity. 12

13 Biodiversity hop:// 13

14 Old Tree of Life Plantae Fungi Animalia Pro/sta Monera 14

15 New Tree of Life Prokaryotes Eukaryotes Bacteria Archaea Eucarya 15

16 Almost ALL of biology is Microbiology! Prokaryotes Eukaryotes Bacteria Archaea Eucarya Microbial 16

17 What do microbes do? Paved the way for the evolugon of life on Earth as we know it. Fix the most carbon and all the nitrogen. Produce the most oxygen. Display incredible diversity in where they can live, what they can eat, and the chemicals they can produce: some eat toxins, breathe uranium, thrive in hot springs, freezing oceans, or acid mine drains. Form symbioses, build communiges, communicate, cooperate, and prey on each other. Many cause disease, but many many more play posigve roles in the health of humans and the planet. May help solve challenges facing humankind. 17

18 Microbial biology can be harnessed by humans Food Microbiology Biofuel ProducGon BioremediaGon Bioterrorism 18

19 Outline I. Microbiology overview II. Bacterial communicagon Quorum sensing Cell cell communicagon during Bacillus sub*lis sporulagon 19

20 Vibrio fischeri: A bioluminescent bacterium 20

21 Vibrio fischeri: A bioluminescent bacterium Image courtesy of the Bassler Lab 21

22 Symbiosis: Vibrio fischeri and the Hawaiian Bobtailed Squid Image courtesy of University of Wisconsin Madison Hawaiian Bobtailed Squid 22

23 The Hawaiian Bobtailed Squid light organ light organ Modified from Koropatnick et al. (2004) 23

24 Counter illuminagon while hungng in moonlight anneoeillustragon.com 24

25 Bacterial luciferase (enzyme) faoy aldehyde faoy acid + O 2 + FMNH 2 + H 2 O + FMN Light! 25

26 26

27 Nealson et al. 1970, Figure 2: cell density bioluminescence 27

28 Conclusions: At low cell density, cells do not produce light. At high cell density, cells rapidly (and in unison) turn on light producgon. This requires transcripgon (If add inhibitors that block transcripgon, don t see light) How do the bacteria coordinate their behavior at a specific density? How do the bacteria know their density?!?!? 28

29 ? 29

30 What is condigoned medium? Fresh growth medium 30

31 What is condigoned medium? Fresh growth medium 31

32 What is condigoned medium? Fresh growth medium 32

33 What is condigoned medium? Remove cells by filtragon Fresh growth medium Condi/oned medium 33

34 CondiGoned medium experiment Fresh growth medium CondiGoned medium 34

35 CondiGoned medium experiment Low density High density Fresh medium OFF ON 35

36 CondiGoned medium experiment Low density High density Fresh medium OFF ON CondiGoned medium ON ON 36

37 Evidence for secreted chemical signals! Fresh growth medium * * * * * * * * * * * * * * * * * * * * * CondiGoned medium * = secreted signaling molecule Auto inducer 37

38 What is the auto inducer? Homo serine lactone A bacterial pheromone! 38

39 Quorum sensing 39

40 Quorum sensing 40

41 Quorum The minimum number of members required for a group to officially conduct business and to cast binding votes 41

42 CriGcal features of quorum sensing 1. Cells are constantly producing the secreted signal. 2. Cells are constantly detecgng the signal. 3. At low concentragons of the signal (indicagng a low density of cells), the cells do not respond. 4. Once a threshold concentragon of signal is present (indicagng a high density of cells), each cell responds by acgvagng genes (in this case, the gene encoding luciferase). 42

43 Quorum sensing and the Vibrio fischeri / squid symbiosis From Nyholm and McFall Ngai (2004) 43

44 Many bacteria harbor quorum sensing systems 44

45 Many bacteria harbor quorum sensing systems 45

46 Many molecules can be used as autoinducers 46

47 Quorum sensing controls many biological processes 47

48 Quorum sensing controls many biological processes 48

49 Quorum sensing controls many biological processes 49

50 Staphylococcus aureus S. aureus can cause disease in nearly every organ and tissue, but usually only in immunocompromised patients. Many healthy individuals are asymptomatic carriers. In the community, most S. aureus infections are skin infections. Variants of S. aureus have emerged that are resistant to several antibiotics: MRSA (Methicillin-resistant Staphylococcus aureus) 50

51 Control of virulence by quorum sensing Low cell density High cell density 51

52 Novel angbiogcs that block quorum sensing?!!! 52

53 Many bacteria harbor quorum sensing systems Made by many bacteria = Bacterial Esperanto? 53

54 More ingmate bacterial communicagon? Amazing, intricate, elaborate bacterial communiges! 54

55 Bacillus sub*lis sporulagon * * * V S * * * V S S V 55

56 Bacillus sub*lis spore formagon Asymmetric division Engulfment 56

57 Forespore engulfment animagon (2D) 57

58 Forespore engulfment animagon (3D) 58

59 SporulaGon transcripgon factors are cell specific mother cell σ F forespore Pσ E gfp σ E σ G Pσ G gfp σ K 59

60 The mother cell and forespore communicate mother cell forespore σ F 60

61 The mother cell and forespore communicate mother cell forespore σ E σ F 61

62 The mother cell and forespore communicate mother cell forespore σ E σ F σ E 62

63 The mother cell and forespore communicate mother cell forespore σ E σ F σ E σ G 63

64 The mother cell and forespore communicate mother cell forespore σ E σ F σ E σ G σ G 64

65 The mother cell and forespore communicate mother cell forespore σ E σ F σ E σ G σ K σ G 65

66 The mother cell and forespore communicate mother cell forespore σ E σ F σ E σ G σ K σ G 66

67 Cell cell communicagon leading to σ K acgvagon Mother cell Forespore pro σ K Protease σ G σ K Signaling protein 67

68 σ G acgvagon has remained mysterious mother cell forespore σ E σ F σ E σ G σ K σ G 68

69 An unexpected form of cell cell communicagon! mother cell forespore σ E σ F σ E σ G We think the mother cell is feeding the forespore!!! σ K σ G 69

70 Shriveled forespores in the absence of the channel Wild Type Channel mutants (from Doan et al (2009) PLOS Genetics 5: e )

71 Feeding tube model Nutrient/energy availability in the forespore 71

72 Feeding tube model Nutrient/energy availability in the forespore nutrients? amino acids? ATP? σ G 72

73 Take home messages Most of biology is microbiology. The answers to some of the most important challenges facing humankind may be found in microbiology. Bacteria communicate extensively with one another, both at a distance and in close range. Molecules that disrupt bacterial communicagon may provide new classes of angbiogcs. 73

74 Want to learn more? BIOS 324. Microbiology An examinagon of microbial life, including archaea, bacteria, fungi, and progsts. Viruses will also be considered. Emphasis on the molecular genegcs of microbes and their relagonship to the origin of life, human health and medicine, and the environment. 74