Lecture 6

Question 1

what do B. theta and B. caccae prefer to break down?

Answer 1

Bt prefers levan over insulin, B. caccae is the opposite.

Question 2

what happens when mice are colonised with Bt and B. caccae and fed insulin?

Answer 2

the B. caccae outcompetes Bt and ‘wins’.

Question 3

what conclusions are made from the Bt and B. caccae studies?

Answer 3

glycan preference seems to predict competitiveness, but its possible that its not glycan preference but another factor driving it.

Question 4

what happened when the B. caccae insulin PUL was transplanted into Bt?

Answer 4

the transplanted Bt strain can now compete in an insulin environment with B. caccae.

Question 5

what is the infant gut dominated by pre weaning?

Answer 5

Bifidobacterium spp. especially B. infantis

Question 6

what does human milk contain large numbers of?

Answer 6

contains large numbers of complex oligosaccharides (HMOs). Bifidos are known to be very good at using HMOs that’s why there’s high Bifidobacteria levels pre weaning. (70%).

Question 7

what has been added to formula milk for women who don’t breastfeed?

Answer 7

HMOs.

Question 8

what bacteria can also use HMOs?

Answer 8

Bacteroides but they don’t dominate the gut.

Question 9

what happens when Bt and B. infantis compete in a mucin environment?

Answer 9

Bt thrives and grows well with not much B. infantis growth.

Question 10

what happens when Bt and B. infantis are grown in a mix of different oligosaccharides?

Answer 10

both bacteria thrive and grow well.

Question 11

what is Lacto-N-neotetraose? (LNnT)

Answer 11

a specific HMO found within breastmilk.

Question 12

what happens when Bt and B. infantis are grown in an LNnT environment?

Answer 12

bifido infantis thrives because it has specificity to LNnT.

Question 13

why do we want to maintain Bacteroides in the infant gut too?

Answer 13

we want them in the post weaning gut so that the becteroides are already there and don’t have to arrive to the body.

Question 14

what happens to the microbiota in a low-fibre diet?

Answer 14

mucin-degrading bacteria increase. the diversity of microbiota decreases.

Question 15

what happened in mouse models when a mouse with a low-fibre diet was switched to a high fibre diet?

Answer 15

the degree of microbiota recovery decreased, implying extinction of some microbial species.

Question 16

what was the microbiota like in the offspring of a low fibre diet mouse?

Answer 16

in generation 2, there was further receded microbial diversity, in generation 3 (generation 2 offspring), there was even more reduced diversity.

Question 17

what was the microbiota recovery in generations 2 and 3 mice when switched to a high-fibre diet?

Answer 17

egeneration 2 showed less recovery and generation 3 showed even less recovery and still had a low microbiota diversity.

Question 18

where does the main evidence of the role of fibre in microbial diversity come from?

Answer 18

the analysis of people from traditional non-industrial societies where levels of fibre intake are much higher then in the western ‘industrialised’ world.

Question 19

what is the microbiome like in people from non-industrialised societies?

Answer 19

they have a higher microbiota diversity, and almost no chronic diseases like IBD and colo-rectal cancer.

Question 20

what happens to indigenous people who move to a western country or adapt a wester lifestyle?

Answer 20

they have higher incidences of IBD and CRC due to reduced microbiota diversity.