TABLE 1.

Oligonucleotide probes used in this study and fraction of total cells detected in the spring sample of coastal North Sea water^a

Probe	Sequence (5′ → 3′)	Target organisms	Reference	Hybridized fraction (%)c
EUB338	GCT GCC TCC CGT AGG AGT	Domain Bacteria	2	91 ± 1.3
NON338	ACT CCT ACG GGA GGC AGC	Complementary to EUB338	2	<1
ALF968	GGT AAG GTT CTG CGC GTT	Most α-proteobacteria	17	26.7 ± 1.4
ROS537	CAA CGC TAA CCC CCT CC	Roseobacter spp. and SAR83 α-proteobacteria	12a	11.0 ± 0.1
BET42ab	GCC TTC CCA CTT CGT TT	β-Proteobacteria	28a	9.3 ± 3.1
OM43-162	ATG CGG CAT TAG CTA ACC	OM43 clade of β-proteobacteria	This study	4.0 ± 0.2
Nso190	CGA TCC CCT GCT TTT CTC C	Ammonia-oxidizing β-proteobacteria	31	3.4 ± 0.2
Nso1225	CGC CAT TGT ATT ACG TGT GA	Ammonia-oxidizing β-proteobacteria	31	4.0 ± 0.4
GAM42ab	GCC TTC CCA CAT CGT TT	γ-Proteobacteria	28a	20.0 ± 1.4
SAR86-1245	TTA GCG TCC GTC TGT AT	SAR86 cluster of γ-proteobacteria	55a	15.2 ± 0.2
CF319a	TGG TCC GTG TCT CAG TAC	Cytophaga-Flavobacterium	28	29.1 ± 3.8

^aA formamide concentration of 55% was used in the hybridization buffer for all the probes. Hybridization and washing were performed at 35 to 37°C except for probe Nso190 (hybridization at 46°C and washing at 48°C). The concentration of sodium chloride in the washing buffer was 10 mM except for probe Nso190 (20 mM).

^bUsed with an equimolar amount of unlabeled competitor oligonucleotides.

^cMeans ± standard deviations for triplicate determinations.