Detection of the nifH gene of Methanobrevibacter smithii: a potential tool to identify sewage pollution in recreational waters.
OBJECTIVE
The goal of this study was to develop and test the efficacy of a PCR assay for the environmental detection of the nifH gene of Methanobrevibacter smithii, a methanogen found in human faeces and sewage.


RESULTS
PCR primers for the nifH gene of M. smithii were designed, tested and used to detect the presence or absence of this organism in faecal and environmental samples. Specificity analysis showed that the Mnif primers amplified products only in M. smithii pure culture strains (100%), human faeces (29%), human sewage samples (93%) and sewage-contaminated water samples (100%). No amplification was observed when primers were tested against 43 bacterial stock cultures, 204 animal faecal samples, 548 environmental bacterial isolates and water samples from a bovine waste lagoon and adjacent polluted creek. Sequencing of PCR products from sewers demonstrated that a 222-bp product was the nifH gene of M. smithii. The minimal amount of total DNA required for the detection of M. smithii was 10 ng for human faeces, 10 ng for faecally contaminated water and 5 ng for sewage. Recreational water seeded with M. smithii established a lower detection limit of 13 cells ml(-1).


CONCLUSIONS
The Mnif assay developed during this investigation showed successful detection of M. smithii in individual human faecal samples, sewage and sewage-contaminated water but not in uncontaminated marine water or bovine-contaminated waters. The Mnif assay appears to be a potentially useful method to detect sewage-polluted coastal waters.


CONCLUSIONS
This study was the first to utilize methanogens as an indicator of sewage pollution. Mnif PCR detection of M. smithii was shown to be a rapid, inexpensive and reliable test for determining the presence or absence of sewage pollution in coastal recreational waters.
Ufnar
J A
JA
Department of Biological Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406-0001, USA.
Wang
S Y
SY
Christiansen
J M
JM
Yampara-Iquise
H
H
Carson
C A
CA
Ellender
R D
RD
D000818:Animals; D001483:Base Sequence; D002417:Cattle; D017931:DNA Primers; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water; D006801:Humans; D041581:Methanobrevibacter / Q000235:genetics*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D012722:Sewage; D014871:Water Microbiology; D014876:Water Pollution
D017931:DNA Primers; D012722:Sewage; D010088:Oxidoreductases; C029130:nitrogenase reductase