Methods and kits for identifying microorganisms in a sample
Disclosed herein are compositions with uniquely designed oligonucleotide primers for identifying a plurality of microorganisms in a sample, and improved methods for detection of microbial populations from diverse biological and environmental samples.
1. A composition comprising a mixture of a forward primer set and a reverse primer set for identifying a plurality of microorganisms in a sample, wherein each primer set comprises one or more oligonucleotide primers, and at least one set comprises multiple primers;
each primer comprises a domain-specific sequence that is substantially complementary to a conserved domain of a bacterial or archaeal ribosomal 16S DNA sequence adjacent to the V3, V4, or V5 region of said 16S DNA sequence; and
for each primer set comprising multiple primers, the primers within the set are overlapping primers which are substantially complementary to the same conserved domain, and each primer within the set differs from at least another primer within the set by a frame shift of one to three nucleotides at the 5′ end of the domain-specific sequence, such that said forward primer set and said reverse primer set generate frame-shifted amplicons in a polymerase-chain reaction (PCR), and wherein each primer in said composition further comprises an at least partial adapter sequence for facilitating sequencing of said sequence.
2. The composition of claim 1 , wherein each primer in said primer set comprising multiple primers further comprises at least one random nucleotide adjacent to the 5′ start of the domain-specific sequence.
3. The composition of claim 1 , wherein the frame-shifted amplicons generated include amplicons comprising (i) the V3 and V4 regions; (ii) the V4 and V5 regions; (iii) the V4 region, and/or (iv) the V3, V4, and V5 regions.
4. The composition of claim 1 , wherein the domain-specific sequence of each primer of the forward primer set is substantially complementary to the C2-domain of said 16S DNA sequence, and wherein the domain-specific sequence of each primer of the reverse primer set is substantially complementary to the C4-domain of said 16S DNA sequence.
5. The composition of claim 1 , wherein the domain-specific sequence of each primer of the forward primer set is substantially complementary to the C3-domain of said 16S DNA sequence, and wherein the domain-specific sequence of each primer of the reverse primer set is substantially complementary to the CS-domain of said 16S DNA sequence.
6. The composition of claim 1 , wherein both the forward primer set and the reverse primer set comprise multiple overlapping primers.
7. The composition of claim 6 , comprising:
a first set of forward, overlapping primers, wherein the domain-specific sequence of each primer of the first forward primer set is substantially complementary to the C2-domain of said 16S DNA sequence;
a second set of forward, overlapping primers, wherein the domain-specific sequence of each primer of the second forward primer set is substantially complementary to the C3-domain of said 16S DNA sequence;
a first set of reverse, overlapping primers, wherein the domain-specific sequence of each primer of the first reverse primer set is substantially complementary to the C4-domain of said 16S DNA sequence; and
a second set of reverse, overlapping primers, wherein the domain-specific sequence of each primer of the second reverse primer set is substantially complementary to the CS-domain of said 16S DNA sequence,
such that the frame-shifted amplicons generated include amplicons comprising the V4 region, amplicons comprising the V3 and V4 regions, amplicons comprising the V4 and V5 regions, and amplicons comprising the V3, V4, and V5 regions.
8. The composition of claim 1 , further comprising at least one pair of forward and reverse adapter oligonucleotide primers that are substantially complementary to the at least partial adapter sequence of said oligonucleotide primers.
9. The composition of claim 8 , further comprising at least one pair of forward and reverse universal oligonucleotide primers that are substantially complementary to the adapter oligonucleotide primers.
10. The composition of claim 1 , wherein said oligonucleotide primers are selected from the group consisting of SEQ ID NO: 2 through SEQ ID NO: 20.
11. The composition of claim 10 , wherein said composition comprises two or more oligonucleotide forward primers selected from SEQ ID NOS: 2, 3, 4, 5, 6, 7, 8, 16, and 17, and two or more oligonucleotide reverse primers selected from SEQ ID NOS: 9, 10, 11, 12, 13, 14, 15, 18, 19, and 20.
12. The composition of claim 11 , wherein said composition comprises two or more oligonucleotide forward primers selected from SEQ ID NOS: 2, 3, 4, 5, and 16, and two or more oligonucleotide reverse primers selected from SEQ ID NOS: 9, 10, 11, 12, 13, and 18, for amplification of V3 to V4 regions.
13. The composition of claim 12 , wherein said composition comprises two or more oligonucleotide forward primers selected from SEQ ID NOS: 6, 7, 8, and 17, and two or more oligonucleotide reverse primers selected from SEQ ID NOS: 14, 15, 19, and 20, for amplification of V4 to V5 regions.
14. A method to identify a plurality of microorganisms in a sample, the method comprising:
a. amplifying DNA from said sample with a forward primer set and a reverse primer set, each primer set comprising one or more oligonucleotide primers, and at least one set comprises multiple primers; each primer comprising a domain-specific sequence that is substantially complementary to a conserved domain of a bacterial or archaeal ribosomal 16S DNA sequence adjacent to the V3, V4, or V5 region of said 16S DNA sequence; and wherein for each primer set comprising multiple primers, the primers within the set are overlapping primers which are substantially complementary to the same conserved domain, and each primer within the set differs from at least another primer within the set by a frame shift of one to three nucleotides at the 5′ end of the domain-specific sequence, such that said forward primer set and said reverse primer set generate frame-shifted amplicons;
b. isolating the generated frame-shifted amplicons from the amplified DNA;
c. sequencing the isolated amplicons; and
d. identifying microorganisms present in said sample based on identification of species-specific 16S DNA sequences in the amplicons generated from said sample.
15. The method of claim 14 , wherein each primer in said primer set comprising multiple primers further comprises at least one random nucleotide adjacent to the 5′ start of the domain-specific sequence.
16. The method of claim 14 or 15 , wherein each primer in said primer set comprising multiple primers further comprises at least one degenerate nucleotide within the domain-specific sequence.
17. The method of claim 14 , wherein the oligonucleotide primers in step (a) comprise:
a first set of forward, overlapping primers, wherein the domain-specific sequence of each primer of the first forward primer set is substantially complementary to the C2-domain of said 16S DNA sequence;
a second set of forward, overlapping primers, wherein the domain-specific sequence of each primer of the second forward primer set is substantially complementary to the C3-domain of said 16S DNA sequence;
a first set of reverse, overlapping primers, wherein the domain-specific sequence of each primer of the first reverse primer set is substantially complementary to the C4-domain of said 16S DNA sequence; and
a second set of reverse, overlapping primers, wherein the domain-specific sequence of each primer of the second reverse primer set is substantially complementary to the C5-domain of said 16S DNA sequence,
such that the frame-shifted amplicons generated in step (a) include amplicons comprising the V4 region, amplicons comprising the V3 and V4 regions, amplicons comprising the V4 and V5 regions, and amplicons comprising the V3, V4 and V5 regions.
18. The method of claim 17 , wherein said amplification step (a) comprises:
i. amplifying DNA from a portion of said sample using said first set of forward, overlapping primers and the first set of reverse, overlapping primers to generate amplicons comprising the V3 and V4 regions;
ii. amplifying DNA from a different portion of said sample using said second set of forward, overlapping primers and said second set of reverse, overlapping primers to generate amplicons comprising the V4 and V5 regions;
iii. pooling the reaction mixtures from steps (i) and (ii); and
iv. amplifying DNA in the pooled mixture to generate a library of frame-shifted amplicons which include amplicons comprising the V3 and V4 regions, amplicons comprising the V4 and V5 regions, amplicons comprising the V4 region, and amplicons comprising the V3, V4, and V5 regions.
19. The method of claim 18 , wherein each of the oligonucleotide primers further comprise an at least partial adapter sequence.
20. The method of claim 19 , wherein adapter primers and universal primers are added to the pooled reaction mixture of step (iii) prior to performing DNA amplification in step (iv).
21. The method of claim 18 , wherein said DNA amplification in step (i) and (ii) each comprises eight to twelve cycles of PCR, and the DNA amplification in step iv comprises five to seven cycles of PCR.
22. The method of claim 19 , wherein said amplified DNA is sequenced using dye sequencing or pyrosequencing.
23. The compostion of claim 1 , wherein each primer in said primer set comprising multiple primers further comprises at least one degenerate nucleotide within the domain-specific sequence.