TABLE 2.

Comparison of sediment and hydrothermal vent isolates of the marine alpha-proteobacterial cluster

Strain	Origin of sample	Dilution (ml−1) at point of isolation	Respiration substratea	NO3− reduction	Growth temperature (°C)	SO42− produced (mM)b	pH decrease on S2O32−c	SO42− produced (mM) without and with 10 mM pyruvated	DGGE group
AIII3	0-1 cm abyssal sed.e	10−3	O2		15, 24	4.54	1.7–1.8	4.2/5.05	I
DI4	0-1 cm slope sed.	10−4	O2		15, 24	4.46	0.7–1.0	2.41/2.49	II
DII3	0-1 cm slope sed.	10−3	O2, NO3−	NO2−	15, 24	2.26	0.8–0.9	2.24/1.04	II
DIII3	0-1 cm slope sed.	10−3	O2, NO3−	NO2−	15, 24	1.97	0.6–0.7	2.55/1.12	II
EI2	1-2 cm slope sed.	10−2	O2		15, 24	2.98	0.6–0.7	1.71/0.2	III
DI4*	0-1 cm slope sed.	10−4	O2		15, 24	4.46	0.5–0.6	1.97/1.22	III
EI1*	1-2 cm slope sed.	10−1	(O2), NO3−	N2	15, 24	2.28	0.7–0.8	1.14/7.31	IV
DIII4*	0-1 cm slope sed.	10−4	(O2), NO3−	N2	15, 24	2.14	0.6–0.7	0.44/4.76	IV
NF18	Beggiatoa mat, Galapagos vents		O2, NO3−	NO2−	15, 24, 37, 42	4.38	1.5–1.6	3.51/9.29	V
AG33	Water sample, Galapagos vents		O2, NO3−	NO2−f	15, 24, 37, 42	3.45	1.2–1.3	3.80/7.22	VI
TB66	Galapagos vent		O2		15, 24, 37, 42	4.98	1.5–1.6	4.92/9.93	VII

^aParentheses indicate poor growth under air. 

^bAverage of three parallel determinations after 20 days incubation. 

^cThe pH of sterile controls was 7.7 and increased by 0.1 U. The control with the nonthiosulfate oxidizer DIII1c increased by 0.2 pH units. 

^dSeparate experiment; sulfate was determined after 14 days for one sample without pyruvate (left) and one with pyruvate (right). 

^eSed., sediment. 

^fTraces of NO₂⁻; no N₂.