Biogeography of the Hosts

Gutless oligochaetes are an ideal host group for studying the biogeography and evolution of marine symbioses as they occur throughout the world in a wide range of different habitats with some species widely distributed and others highly endemic (Erseus 1992). They are also one of the few marine groups in which such a large number of host species (> 100) are so closely related to each other, forming a monophyletic group with all gutless oligochaetes descendents from a single common ancestor...

Establishment of the Association Differentiation and Behavior of Hormogonia

This general stage can be viewed as three substages (1) induction of hor-mogonium differentiation (2) control of the direction of hormogonium gliding and (3) colonization and repression of hormogonium differentiation. Physiologically, hormogonia are analogous to non-growing swarmer cells of certain prosthecate bacteria, such as Caulobacter crescentus (Roberts et al. 1996 Shimkets and Brun 2000). In response to a variety of environmental signals, including light quality, nutrient stress and the...

The Ciliate Host

Blepharisma

The eukaryotic partners of the consortium are marine, sand-dwelling, hypotrich ciliates. They have been assigned to the Euplotidium genus. Since Noland (1937) erected this genus, six species have been described. Euplotidium itoi and E. arenarium are the only two species characterised at the electron microscopical level. A lateral view of E. itoi at SEM is shown in Fig. 1. The organism is oval in shape, 60-90 m long and 40-52 m wide. The somatic ciliature on the flat ventral surface consists of...

Glycolytic Activities of Mastotermes darwiniensis and its Flagellates

Up to now, it has been believed that the hindgut flagellates produce nutrients using their own cellulolytic enzymes for the benefit of their termite host. The glycolytic activities found in separated cells of Mixotricha paradoxa are compiled in Table 5.3 (Berchtold and K nig, unpubl. res.). Surprisingly, not all of these activities seemed to be produced by the flagellates themselves, but rather taken up with the gut contents. Two endoglucanases, Cel I and Cel II, Monotrichomonas sp....

Symbiont Transmission and Evolution

The evolutionary dynamics between symbiont and host depend largely on the symbiont transmission strategy. Symbiont transmission between successive host generations can occur environmentally (acquisition from a free-living population of symbiotic bacteria), horizontally (transfer between hosts sharing the same habitat), or vertically (transfer from parent to offspring via the egg). Vertically transmitted endosymbionts experience a unique selective regime within the host. These symbionts are...

Characterization of the Microbiota in the Crop of the Leech

The early bacteriological investigations in the 1940s and 1950s described the isolation of a single bacterium from the crop of the medicinal leech (Lehmensick 1941 Hornbostel 1942 Busing 1951 Busing et al. 1953). The consistent isolation of this bacterium and the absence of other microorganisms lead the early investigators to suggest a symbiotic association. Three functions have been proposed for the symbiont (Busing et al. 1953 Graf 2000, 2002) (1) digestion of the ingested blood meal, (2)...

Hydrogen Metabolism

The symbiosis with methanogens is likely based on the interspecies transfer of molecular hydrogen. Little is known about the physiology of the protozoa, but from thermodynamic considerations, any fermentative metabolism releasing part of the reducing equivalents as H2 will become more exergonic if this product is not allowed to accumulate (Schink 1997 see also Chapter by B. Schink). Virtually all 16S rRNA gene clones of methanogens obtained from lower termites fall into the phylogenetic...

Differentiation in Symbiosis

Symbiotic heterocyst differentiation differs from that in the free-living state in at least two ways the signal that activates the differentiation cascade and an enhanced frequency and altered spacing pattern. Signal. Symbiotic heterocyst differentiation is hypothetically independent of the presence and concentration of combined nitrogen in the immediate environment (Meeks 1998, 2003 Meeks and Elhai 2002). Three lines of evidence support this hypothesis. First, approximately 10 M NH4+ represses...

The Digestive Tract Symbiosis of Hirudo medicinalis

In contrast to the digestive tract communities residing in most animals (Savage 1977 Demaio et al. 1996 Lilburn et al. 1999), the digestive tract of Hirudo medicinalis appears to be colonized by a relatively simple microbial community (Lehmensick 1941 Busing et al. 1953 Graf 2000). Only one symbiont, an Aeromonas sp., was consistently cultured in several investigations and culture independent approaches suggest the presence of only a few additional taxa (described below). This apparent...

References

Aeckersberg F, Lupp C, Feliciano B, Ruby EG (2001). Vibrio fischeri outer membrane protein OmpU plays a role in normal symbiotic colonization. J Bacteriol 183 65906597 Boettcher KJ, Ruby EG (1990). Depressed light emission by symbiotic Vibrio fischeri of the sepiolid squid Euprymna scolopes. J Bacteriol 172 3701-3706 Davidson SK, Koropatnick TA, Kossmehl R, Sycuro L, McFall-Ngai MJ (2004) NO means 'yes' in the squid-vibrio symbiosis nitric oxide (NO) during the initial stages of a beneficial...

Vibrio fischeri strains are specifically recruited from the seawater

Vibrio Colonization Squid

V. fischeri comprises less than 0.1 of the total bacterial population in the seawater inhabited by the squid (Lee and Ruby 1992), yet this organism alone K. Geszvain, K. Visick (e-mail kvisick lumc.edu) Dept. Microbiology and Immunology, Loyola University Chicago, 2160 S. First Ave. Bldg. 105, Maywood, IL 60153, USA Progress in Molecular and Subcellular Biology Jorg Overmann (Ed.) Molecular Basis of Symbiosis Springer-Verlag Berlin Heidelberg 2005 is found in the light organ association...

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 Species_Type of symbiontb Habitat_Collection...

Introduction

Nitrogen availability limits the biosynthesis of proteins, amino acids, nucleotides and vitamins in plants more than any other element. Plants assimilate nitrogen as nitrate, and modern agriculture is highly dependent on nitrogenous fertiliser at a global annual cost exceeding 300 million US. Production of nitrogenous fertilisers requires huge energy inputs, and leaching of nitrate causes environmental problems such as contamination of ground water and surface streams (Gresshoff 2003). More...

Morphology of Mixotrixa paradoxa

One of the larger wood-ingesting flagellates in the hindgut of Mastotermes darwiniensis is Mixotricha paradoxa, a member of the order Trichomonadida (Table 5.2). The pear-shaped cells are about 500 m long and 250 m in diameter (Fig. 5.3). The surface of Mixotricha paradoxa shows a highly ordered pattern of rod-shaped bacteria and in addition it is covered by a dense carpet Fig. 5.3. Scanning electron micrograph of Mixotricha paradoxa. The white line indicates the borderline between the anterior...

Specificity of the Symbiosis

A powerful tool for the molecular investigation of a symbiosis is a colonization assay that allows one to evaluate the ability of specific strains to colonize the medicinal leech (Graf 1999, 2002 Indergand and Graf 2000). In order to differentiate the introduced test strain from the native microbiota, we use spontaneous rifampin-resistant mutants as test strains. The strains are added to a blood meal that was preheated to 37 C and is fed to the leech in a parafilm covered disposable centrifuge...

Types of Phototrophic Consortia

To date, a total of 10 morphologically different types of consortia have been detected. Most of them have repeatedly been observed in freshwater habitats. The majority of the phototrophic consortia are round to spindle-shaped, motile, and consist of 13-69 colored cells that form a layer surrounding one colorless central bacterium in the center (Fig. 1B, Fig. 2A,B). Previously, the different types of phototrophic consortia were distinguished based on the color of their epibionts and the...

Prokaryotic Epibionts

Many of the termite gut flagellates are colonized by epibiotic bacteria. Some of the associations are already evident by observation with a light microscope, but only the electron microscope reveals the enormous variety and complexity of these associations (e.g., Cleveland and Grimstone 1964 Leander and Keeling 2004 Figs. 1-3). The presence of special attachment sites on the cell envelope of the flagellates (e.g., Tamm 1980 Radek et al. 1992 Dolan and Margulis 1997 Stingl et al. 2004) indicates...

Modes and Specificity of Interaction between the Bacterial Partners

Theoretically, phototrophic consortia could form randomly from bacterial cells which encounter each other just by chance. Under these conditions, morphologically identical consortia would be expected to harbor different types of green sulfur bacteria and, secondly, free-living epibiont cells should also be detected in the habitat of phototrophic consortia. However, when the epibionts associated with a particular phototrophic consortium were analyzed, all epibi-ont cells invariably contained the...

Phylogenetic Position of Mixotricha paradoxa

Figure 5.4 shows a phylogenetic tree of parabasalids. The SSU rDNA sequences were added to an existing database of 36 parabasalid sequences. This data set included 1,210 nucleotides which were analyzed with distance matrix, maximum parsomony, and maximum likelihood methods (Li 2003). The phylogenetic tree shows that four hindgut protozoa of Mastotermes darwiniensis form one subdivision the small flagellate Metadevescovina extranea and the three large flagellates Koruga bonita, Deltotrichonympha...

Substage 4 Growth and Metabolic Control

The physiological characteristics of Nostoc in symbiotic and free-living growth states are summarized in Table 3. In all plant associations, the Nostoc partners grow obviously slower than do free-living cultures. The mechanistic basis of this growth control is unknown, but it clearly influences the most fundamental developmental direction of N. punctiforme, the vegetative cell cycle. Although the rates of CO2 and NH4+ assimilation are depressed (see below), they are so in proportion to the...

Multiple Bacterial Morphotypes

The first ultrastructural studies of oligochaete symbionts described two bacterial morphotypes (Giere 1981, 1985) large oval bacteria 2-7 m in length filled with sulfur and PHB vesicles and smaller cocci- to rod-shaped bacteria 0.7-1.5 m in length without any conspicuous inclusions or structures in their cytoplasm (Fig. 1) (also see Bright and Giere 2005 for a more detailed review of the ultrastructure of the symbiosis). The large oval bacteria are now known to be sulfur-oxidizing gamma...

The Endomicrobia

For a long time, the nature and identity of the endosymbionts of the larger gut flagellates was completely obscure. Recently, the cytoplasmic symbionts of the hypermastigid Trichonympha agilis and the oxymonad Pyrsonympha vertens in the gut of Reticulitermes santonensis were identified as members of the so-called 'Termite Group 1' (TG-1) (Stingl et al. 2005). Based on their 16S rRNA gene sequences, whose origin was verified by fluorescence in situ hybridization with clone-specific probes, and...

Syntrophic Propionate Oxidation

For syntrophic propionate oxidation according to the equation 4 CH3CH2COO- + 4 H + + 2 H2O 7 CH4 + 5 CO2 A G0' -249 kJ per 4 mol of propionate a metabolic flow scheme can be drawn, leaving a free energy change in the range of -22 to -23 kJ per mol reaction (11 partial reactions) to all partners involved under standard conditions (Stams et al. 1989 Schink 1991), and this values decreases to -19 kJ in laboratory cultures and to -12 kJ at propionate concentrations prevailing in sediments or sludge...

Methane Utilizing Bacteria

The identification of symbionts, since none have been cultured, has depended on comparison with free-living aerobic methanotrophs. Methanotrophic bacteria, unique in their ability to use methane as a substrate, form a subset of methylotrophs, which utilize C1 compounds for energy and carbon acquisition (Anthony 1982). Symbiotic methanotrophs are most closely related to free-living type I aerobic methanotrophs in the gamma Proteobacteria, based on their membrane organization, C1 assimilation...

Inorganic Carbon Acquisition

The Riftia symbiont uses the Calvin cycle for autotrophic carbon fixation and therefore requires access to dissolved organic carbon (DIC) in the form of CO2, the DIC species that diffuses most readily through biological membranes (Fig. 2). While the majority of DIC in seawater (pH 8.0 ) is bicarbonate (HCO3- pKa of 6.1 at in situ temperature and pressure of 10 C and 101.3 kPa Dickson and Millero 1987), the lower pH associated with diffuse flow vents (pH 6.0 around R. pachyptila plumes)...

Discovery of the Riftia pachyptila Symbiosis

Scientific understanding of chemosynthetic symbioses derives in large part from studies of the unique fauna associated with deep-sea hydrothermal vents. Early explorations revealed that, in contrast to common perceptions, the deep benthos was not a cold, food-limited habitat but instead contained flourishing ecosystems localized at hot springs emanating from mid-ocean spreading centers. First characterized along the Galapagos Rift and the East Pacific Rise in the eastern Pacific Ocean,...

Anatomy and Ultrastructure

Riftia pachyptila occurs in dense clumps attached to the seafloor substrate (e.g., basalt) at low flow vents. A narrow, elongate tube composed of chitin and scleroproteins and up to three meters in length protects the soft body of the worm, which is divided into four major regions. The branchial plume lies at the anterior of the worm in direct contact with the surrounding seawater. Infused with blood vessels, this gill-like organ allows an efficient exchange of metabolites (e.g., sulfide,...

The Termite Gut Microecosystem

The symbiotic digestion of lignocellulose by termites is a complex series of events involving both the host and its intestinal microbiota (Brune 2003, 2005). While the digestive activities in the foregut and midgut seem to be mainly caused by the host, the processes in the hindgut are largely controlled by the symbionts. The recalcitrance of the lignocellulosic diet and the dynamics of physicochemical gut conditions contribute to the heterogeneity of ecological niches and are reflected in a...

Hydrogenosomes Organelles that Can Use Protons as Electron Acceptors

In marked contrast to the mitochondrial remnant organelles mentioned above, hydrogenosomes retained an ATP generating function (M ller 1993, 1998). They compartmentalize the terminal reactions of the cellular energy metabolism. Characteristically, hydrogenosomes import pyruvate (or malate) which is oxidatively decarboxylated to acetyl-CoA by the action of a pyru-vate ferredoxin oxidoreductase (PFO), and not, as in aerobic mitochondria, by the action of a pyruvate dehydrogenase (PDH). An acetate...

Pseudocaedibacter

Anderson RM, May RM (1982) Coevolution of hosts and parasites. Parasitology 85 411-426 Anderson RM, May RM (1991) Infectious diseases of humans. Oxford Univ Press, Oxford Atlas RM (1999) Legionella from environmental habitats to disease pathology, detection and control. Environ Microbiol 1 283-293 Balsley M (1967) Dependence of the kappa particles of stock 7 of Paramecium aurelia on a single gene. Genetics 56 125-131 Barker J, Brown MRW (1994) Trojan Horses of the microbial world protozoa and...

The Gut Microenvironment

Based on the oxygen sensitivity and the fermentative metabolism of the intestinal protozoa, the high concentrations of microbial fermentation products, the presence of anaerobic or oxygen-sensitive activities such as methanogenesis and nitrogen fixation, and the isolation of obligately anaerobic bacteria, it was initially assumed that the termite hindgut is an anoxic habitat (for literature, see Breznak 2000 Brune 2005). However, the maintenance of anoxia in an environment of such minute...

The Epibiont

Early electron microscopic studies of phototrophic consortia from the natural samples revealed the presence of chlorosomes in the epibiont cells (Truper and Pfennig 1971 Caldwell and Tiedje 1974), suggesting that they belonged to the group of green sulfur bacteria. This conclusion was supported by the observation that maximum concentrations of green sulfur bacterial pigments (bacterio-chlorophylls c, d and e) in freshwater lakes coincided with population maxima of phototrophic consortia. The...

Evolutionary Ecology of the Caedibacter Symbiosis and R Body Production

Intracellular Bacteria Phylogeny

Intracellular bacteria are favorable for the host and may be regarded as mutu-alists when uninfected competitors are killed due to these bacterial symbionts. This view, however, may be too simple, as ecological and molecular studies revealed fascinating details on the evolutionary ecology of this long known occurrence of killer-bacteria in paramecia. The bacteria are closely related to pathogens and exploit the host cells just as invasive agents in metazoans do. Caedibacter species are energy...

Two Component Signal Transduction Systems

Many bacteria, including V. fischeri, recognize and respond to their environments using two-component regulatory systems (Fig. 2A, reviewed in Stock et al. 2000). These systems are composed of a sensor histidine kinase Fig. 2. Two-component regulatory systems. A. The phospho-relay in orthodox (top) and hybrid (bottom) two-component systems. Upon detection of signal, phosphate generated from a bound ATP is passed from conserved His to Asp residues until finally being transferred to an Asp in the...

Nod Factors

Plants initiate the molecular dialogue with rhizobia by releasing flavonoids into their rhizospheres (Schultze and Kondorosi 1998 Broughton et al. 2003). These flavonoids are then taken up by the bacteria where they bind NodD proteins of the LysR family of transcriptional regulators (Broughton et al. 2000). The promoters of genes relevant for Nod-factor synthesis (nol, noe and nod genes) contain conserved 49 bp motifs called nod-boxes (Feng et al. 2003). NodD proteins bind nod-boxes as...

The Intestinal Microbiota of Mastotermes darwiniensis

The lower wood-feeding termite Mastotermes darwiniensis Froggatt (Fig. 5.1.) is the only living member of the family Mastotermitidae. Today, this species is restricted to Northern Australia, but mastotermitid fossil specimen from the Eocene and Miocene have been found in Central America, the Caribic region, Europe, and Australia (Thorne et al. 2000). Termites are assigned to 13 families and 282 genera (Table 5.1 Myles 1999). Mastotermes darwiniensis is believed to be the most primitive existing...

Substage 3 Colonization and the Repression of Hormogonium Differentiation

Little is known about the actual colonization of the preexisting cavity in the gametophyte tissue of A. punctatus. However, motile hormogonia entering the symbiotic cavities (auricules) of the liverwort Blasia pustilla has been documented (Kimura and Nakano 1990 Adams 2000). Once colonization has taken place, further hormogonium differentiation appears to be suppressed. The isolation of a second N. punctiforme mutant, with the phenotype of a high frequency of infection (Table 1), lead to the...

The Central Bacterium

In the light microscope, the central rod-shaped bacterium can be distinguished from the green or brown epibionts by its greater size, tapered ends, and low phase contrast (compare Fig. 2A, B). It had been proposed that the central bacterium in phototrophic consortia might belong to the sulfate- or sulfur-reducing bacteria (Pfennig 1980). This was based on the experience with cocultures of green sulfur bacteria with sulfur- and sulfate-reducing bacteria, in which the phototrophic component could...

Assignment of 16S rDNA Sequences to the Corresponding Ectosymbiotic Bacterial Morphotypes

By using cell envelope preparations for in situ fluorescence hybridization, an interference with the fluorescence of wood particles was avoided. In addition, the fluorescence signals of the specific Cy3-labelled probes could be enhanced by applying helper oligonucleotides (Fuchs et al. 2000) and the binding of the probes was facilitated by performing a denaturing step. Spirochaeta stenostrepta Spirochete clone MDS1 -Spirochete clone mpsp15 Spirochete clone mp1 - Spirochete clone sp40-8...

Molecular Evolution of R Body Production

Caedibacter endocytobionts of paramecia are infected by phages or plasmids, either of which is responsible for the production of R bodies and probably the toxin (Preer et al. 1972, 1974 Pond et al. 1989 Kusch et al. 2000). Bacterio-phages are evidently non-infective, and bacterial lysis does not seem to occur (Pond et al. 1989), with the exception of Caedibacter caryophilus in the host Paramecium caudatum (Schmidt et al. 1987). The R body coding region of the plasmid of C. taeniospiralis is of...

The Nostoc Bryophyte Symbiotic Experimental System

This chapter will review the results of studies primarily utilizing an association between the nitrogen-fixing cyanobacterium Nostoc punctiforme strain PCC 73102, synonym ATCC 29133 and the bryophyte hornwort Anthoceros punctatus that is routinely reconstituted in the laboratory with the separately pure-cultured partners. The focus will be more on mechanisms of the interaction than on diversity of symbionts the latter is an expanding topic which has recently been examined using molecular...

Hydrogenosomes and Mitochondrial Remnant Organelles Evolved Repeatedly

Tree Mitochondria

Initially, the arguments that both mitosomes, the mitochondrial remnant organelles, and hydrogenosomes evolved several times were based on the observation that hydrogenosomes and mitosomes, respectively, were found in a broad spectrum of rather unrelated taxa of unicellular organisms, such as Fig. 1. Illustration displaying the phylogenetic relationships between aerobic and anaerobic protists based on a variety of molecular data together with a tentative evolutionary tree of mitochondria,...