Method for reducing the population of at least one intestinal and/or gastrointestinal bacteria species comprising bacteriophages, and bacteriophages and the use thereof

1 . A method for reducing the population of at least one intestinal and/or gastrointestinal species of bacteria, the method comprising the following steps:

a) providing a biological sample containing bacteria of at least one intestinal and/or gastrointestinal species of bacteria, the intestinal and/or gastrointestinal species of bacteria directly or indirectly influencing a psychological, neurodegenerative and/or neurological illness and/or disorder of a host organism; and

b) providing bacteriophages of at least one species of bacteriophages that are specific to the intestinal and/or gastrointestinal species of bacteria and that comprise at least one nucleic acid functionally associated with a promoter and/or a regulatory element, the nucleic acid being selected from the group comprising:

i. a nucleic acid sequence coding for at least one antibacterial nucleic acid molecule; and

ii. a nucleic acid sequence encoding a nucleic acid molecule that has at least 90% sequence identity to the nucleic acid molecule encoded by the nucleic acid sequences from i); and

iii. a nucleic acid sequence coding for at least one antibacterial polypeptide; and

iv. a nucleic acid sequence encoding a polypeptide that has at least 90% sequence identity to the polypeptide encoded by the nucleic acid sequences from iii); and

v. a nucleic acid sequence for a fragment of a nucleic acid from i), ii), iii) or iv), the fragment encoding a nucleic acid molecule or a polypeptide; and

c) contacting and incubating the biological sample with the bacteriophages, the incubation continuing until the population of the intestinal and/or gastrointestinal species of bacteria has been reduced by at least 70%;

wherein the intestinal and/or gastrointestinal species of bacteria is anaerobic and/or aerobic and wherein the species of bacteria belongs to Alistipes, Bifidobacterium, Campylobacter, Chlamydia, Desulfovibrio, Enterobacter, Enterobacterium, Faecalibacterium, Helicobacter, Klebsiella, Porphyromonadaceae, Prevotella, Proteus, Roseburia, Ruminococcus, Shigella, Spirochetes, Streptococcus, Treponema or Veillonella ; and wherein the psychological, neurodegenerative and/or neurological illness and/or disorder is a depression, depressive disorder, eating disorder, Parkinson disease, Alzheimer disease, dementia, and/or a mixture thereof.

2 . The method according to claim 1 , wherein step c) is followed by an evaluation of the reduction of the population of the intestinal and/or gastrointestinal species of bacteria.

3 . The method according to claim 1 , wherein the nucleic acid has two or more promoters and/or regulatory elements and/or wherein the nucleic acid encodes nucleic acid sequences for two or more nucleic acid molecules, polypeptides and/or fragments thereof.

4 . A bacteriophage comprising at least one nucleic acid functionally associated with a promoter and/or a regulatory element, the bacteriophage being specific to at least one intestinal and/or gastrointestinal species of bacteria, the intestinal and/or gastrointestinal species of bacteria directly or indirectly influencing a psychological, neurodegenerative and/or neurological illness and/or disorder of a host organism, and the nucleic acid being selected from the group comprising:

a) a nucleic acid sequence coding for at least one antibacterial nucleic acid molecule; and

b) a nucleic acid sequence encoding a nucleic acid molecule that has at least 90% sequence identity to the nucleic acid molecule encoded by the nucleic acid sequences from a); and

c) a nucleic acid sequence coding for at least one antibacterial polypeptide; and

d) a nucleic acid sequence encoding a polypeptide that has at least 90% sequence identity to the polypeptide encoded by the nucleic acid sequences from c); and

e) a nucleic acid sequence for a fragment of a nucleic acid from a), b), c) or d), the fragment encoding a nucleic acid molecule or a polypeptide;

wherein the intestinal and/or gastrointestinal species of bacteria is anaerobic and/or aerobic and wherein the species of bacteria belongs to Alistipes, Bifidobacterium, Campylobacter, Chlamydia, Desulfovibrio, Enterobacter, Enterobacterium, Faecalibacterium, Helicobacter, Klebsiella, Porphyromonadaceae, Prevotella, Proteus, Roseburia, Ruminococcus, Shigella, Spirochetes, Streptococcus, Treponema or Veillonella , and wherein the psychological, neurodegenerative and/or neurological illness and/or disorder is a depression, depressive disorder, eating disorder, Parkinson disease, Alzheimer disease, dementia, and/or a mixture thereof.

5 . The bacteriophage according to claim 4 , wherein the nucleic acid has two or more promoters and/or regulatory elements and/or wherein the nucleic acid encodes nucleic acid sequences for two or more nucleic acid molecules, polypeptides and/or fragments thereof.

6 . The bacteriophages according to claim 4 and/or a pharmaceutical composition comprising bacteriophages according to claim 4 and at least one other ingredient for use as a drug for changing the composition of the gut microbiota, as a drug for preventing the development and/or decelerating the progression of the psychological, neurodegenerative and/or neurological illness and/or disorder and/or as a drug for treating the psychological, neurodegenerative and/or neurological illness and/or disorder.

7 . The bacteriophages according to claim 4 and/or a pharmaceutical composition comprising bacteriophages according to claim 4 and at least one other ingredient for use in treating the psychological, neurodegenerative and/or neurological illness and/or disorder.

8 . The bacteriophages according to claim 4 and/or a pharmaceutical composition comprising bacteriophages according to claim 4 and at least one other ingredient for use in a therapeutic method or in a non-therapeutic method for changing the composition of the gut microbiota, in a therapeutic method or in a non-therapeutic method for preventing the development and/or decelerating the progression of the psychological, neurodegenerative and/or neurological illness and/or disorder and/or in a therapeutic method or in a non-therapeutic method for treating the psychological, neurodegenerative and/or neurological illness and/or disorder.