Methanotrophic Symbioses

Methanotrophic endosymbioses have only been characterized in a few marine invertebrate taxa and deep-sea habitats. Symbioses involving methanotrophs were first described in bathymodioline mussels inhabiting deep-sea cold seeps (Childress et al. 1986; Cavanaugh et al. 1987) and subsequently found in other bathymodioline mussels, a pogonophoran

Table 1. The taxonomic and biogeographic distribution of methanotroph-hosting invertebrates"

Host phylum Family Subfamily

Species_Type of symbiontb Habitat_Collection sites0_References'1

Mollusc Mytilidae

Bathymodiolinae

Bathymodiolus

M

Seep/vent

WP

Okinawa Trough, Sagami

1,2

japonicus

Bay

B. platifrons

M

Seep/vent

WP

Okinawa Trough, Sagami

2, 3

Bay

B. childressi

M

Seep

AG

Alaminos Canyon, Florida

4, 5, 6

Escarpment

B. boomerang

M, C

Seep

A

Barbados Trench

7

B. brooksi

M, C

Seep

A

Alaminos Canyon

8,9

B. heckerae

M, C

Seep

A,AG

Blake Ridge, Florida

10-12

Escarpment

B. azoricus

M, C

Vent

A

Mid-Atlantic Ridge

13-15

B. puteosercpentis

M, C

Vent

A

Mid-Atlantic Ridge

15-18

B. sp. Gabon margin

M, C

Seep

A

Gabon Margin

19

B. thermophilus

C

Vent

EP

Eastern Pacific Rise

20,21

B. sp. Juan de Fuca

c

Vent

EP

Juan de Fuca

22

B. aduloides

c

Seep

WP

Okinawa Trough

23

B. septemdierum

c

Seep

WP

Okinawa Trough

2, 23

B. elongates

c

Vent

WP

Lau and Fiji Basins

24

B. brevior

c

Vent

WP

Lau and Fiji Basins

25

B. aff. brevior

c

Vent

I

Central Indian Ridge

26-28

(=B. mariscindicus)

(=B. mariscindicus)

Host phylum Family Subfamily

Species Type of symbiontb Habitat Collection sites0 References4

Tamu fisheri C Seep AG Louisiana Slope 29

Annelida Siboglinidae

Siboglinumposeidoni M Seep A Skagerrak, North Atlantic 30

Porifera Cladorhizidae

Cladorhiza M Seep A Barbados Trench 31

methanophila

"Known species of deep-sea vent and seep bathymodioline mussels are listed to highlight that these mussels can host methanotrophs, chemoautotrophs, or both types of bacterial symbionts. The presence and characterization of symbionts is based on several techniques, including transmission electron microscopy, enzyme assays, radiolabeled uptake experiments, 16S rRNA sequence data, and/or in situ hybridization of symbiont-specific gene probes bType of symbiont: C chemoautotroph; Mmethanotroph

'Collection sites abbreviated as follows: A Atlantic; / Indian; AG Atlantic, Gulf of Mexico, EP Eastern Pacific, WP Western Pacific

"References - 'Hashimoto and Okutani (1994); 2Fujiwara et al. (2000); 3Barry et al. (2002); "Childress et al. (1986); 5Fisher et al. (1987); 6Kochevar et al. (1992); 7von Cosel and Olu (1998); 8Fisher et al. (1993); 'Gustafson et al. (1998); 10Cavanaugh et al. (1987); "Cary et al. (1988); 12Cavanaugh

(1992); "Trask and van Dover (1999); 14Fiala-Medioni et al. (2002); 15Pimenov et al. (2002); 16Cavanaugh et al. (1992); "Distel et al. (1995);

18Robinson et al. (1998); "Duperron et al. (2005a); 20Belkin et al. (1986); 21Nelson et al. (1995); 22McKiness et al. (2005); 23Yamanaka et al. (2000);

24Pranal et al. (1997); 25Dubilier et al. (1998); 26van Dover et al. (2001); 27Yamanaka et al. (2003); 28McKiness and Cavanaugh (2005); 29MacAvoy et al. (2005); 30Schmaljohann (1991); 31Vacelet et al. (1996)

tubeworm, and carnivorous sponges at seeps and hydrothermal vents (Table 1). The symbioses were identified based on the co-occurrence of bacteria containing intracytoplasmic membranes typical of type I methanotrophs and assays for enzymes diagnostic of methylotrophy (e.g., methanol dehydrogenase). Bathymodiolus childressi (Fig. 2a), from hydrocarbon seeps on the Louisiana Slope, Gulf of Mexico, was the first species found to house bacteria that exhibit intracytoplasmic membranes typical of type I methanotrophs, while the dual symbiosis was first described in B. heckerae, as observed through transmission electron microscopy (Childress et al. 1986; Cavanaugh et al. 1987). The methane oxidizing nature of the bacteria was confirmed through radiolabeled 14C-methane uptake experiments that measure the amount of 14CH4 incorporated into acid-stable compounds and CO2 and through methanol dehydrogenase (MeDH) assays that detect the activity of a key enzyme in the methane oxidation pathway (Cavanaugh et al. 1987; Fisher et al. 1987; Cavanaugh 1992). Subsequently, invertebrates from other methane-rich environments have been examined with a suite of techniques aimed at detecting symbiotic methanotrophs, such as additional enzyme assays, stable carbon isotope analysis (comparing 138C values), phylogenetic analysis of 16S rRNA sequence data, and in situ hybridization of symbiont-specific genetic probes.

Was this article helpful?

0 0

Post a comment