COMPOSITIONS COMPRISING BACTERIAL STRAINS

1 .- 39 . (canceled)

40 . A method of increasing the microbiota diversity in a subject in need thereof, comprising administering to the subject a pharmaceutical composition comprising a therapeutically effective amount of a bacterial strain of the species Bacteroides thetaiotaomicron , wherein the bacterial strain comprises a 16S rRNA gene sequence that has at least 95% sequence identity to a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 1-12, and a pharmaceutically acceptable excipient or carrier.

41 . The method of claim 40 , wherein the administering causes an increase in the number of the sequence-based bacterial classifications or Operational Taxonomic Units (OTUs) in the subject's microbiota, or an increase in the Shannon Diversity Index of the subject's microbiota.

42 . The method of claim 40 , wherein the subject has been tested and found to have a reduced level of microbiota diversity relative to a healthy subject.

43 . The method of claim 42 , wherein the subject has fewer than 99 different bacterial species and/or less than 190 different bacterial strains in its microbiota.

44 . The method of claim 40 , wherein the subject has a disease or disorder associated with a reduced level of microbiota diversity compared to a healthy subject.

45 . The method of claim 44 , wherein the disease or disorder comprises irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), obesity, type 2 diabetes, an infectious disease, cancer, an allergic disease, an autoimmune disease, or a metabolic disease.

46 . The method of claim 44 , wherein the disease or disorder is Crohn's disease.

47 . The method of claim 40 , wherein the increasing the microbiota diversity comprises increasing acetogenic bacteria or non-acetogenic bacteria.

48 . The method of claim 40 , wherein the microbiota diversity is increased in the intestine of the subject.

49 . The method of claim 40 , wherein the microbiota diversity is increased in the distal gut of the subject.

50 . The method of claim 40 , wherein the pharmaceutical composition is formulated for oral administration.

51 . The method of claim 40 , wherein the bacterial strain is lyophilised.

52 . The method of claim 40 , wherein the bacterial strain is viable.

53 . The method of claim 40 , wherein the pharmaceutical composition is formulated as a tablet, a capsule, or powder.

54 . The method of claim 40 , wherein the pharmaceutical composition comprises a single strain from the genus Bacteroides.

55 . The method of claim 40 , wherein the sequence identity is determined by a Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2.

56 . The method of claim 40 , wherein the bacterial strain comprises a 16S rRNA gene sequence that has at least 98% sequence identity to the polynucleotide sequence selected from the group consisting of SEQ ID NOs: 1-12, as determined by a Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2.

57 . The method of claim 40 , wherein the bacterial strain comprises a 16S rRNA gene sequence that has at least 95% sequence identity to the sequence of SEQ ID NO: 1, as determined by a Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2.

58 . The method of claim 40 , wherein the bacterial strain is the strain deposited under accession number 42341 at NCIMB.

59 . A method of inducing the microbiota stability in a subject in need thereof, the method comprising administering to the subject a pharmaceutical composition comprising a bacterial strain of the species Bacteroides thetaiotaomicron , wherein the bacterial strain comprises a 16S rRNA gene sequence that has at least 95% sequence identity to a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 1-12.