Chemical structure of the cell wall polymer of methanosarcina

Cell walls, a comparative view of the composition of cell surfaces of plants, algae and microorganisms

While evolutionary studies indicate that the most ancient groups of organisms on Earth likely descended from a common wall-less ancestor, contemporary organisms lacking a carbohydrate-rich cell surface are exceedingly rare. By developing a cell wall to cover the plasma membrane, cells were able to withstand higher osmotic pressures, colonise new habitats and develop complex multicellular structures. This way, the cells of plants, algae and microorganisms are covered by a cell wall, which can generally be defined as a highly complex structure whose main framework is usually composed of carbohydrates. Rather than static structures, they are highly dynamic and serve a multitude of functions that modulate vital cellular processes, such as growth and interactions with neighbouring cells or the surrounding environment. Thus, despite its vital importance for many groups of life, it is striking that there are few comprehensive documents comparing the cell wall composition of these groups. Thus, the aim of this review was to compare the cell walls of plants with those of algae and microorganisms, paying particular attention to their polysaccharide components. It should be highlighted that, despite the important differences in composition, we have also found numerous common aspects and functionalities.

Spotlight on FtsZ-based cell division in Archaea

Compared with the extensive knowledge on cell division in model eukaryotes and bacteria, little is known about how archaea divide. Interestingly, both endosomal sorting complex required for transport (ESCRT)-based and FtsZ-based cell division systems are found in members of the Archaea. In the past couple of years, several studies have started to shed light on FtsZ-based cell division processes in members of the Euryarchaeota. In this review we highlight recent findings in this emerging field of research. We present current knowledge of the cell division machinery of halophiles which relies on two FtsZ proteins, and we compare it with that of methanobacteria, which relies on only one FtsZ. Finally, we discuss how these differences relate to the distinct cell envelopes of these two archaeal model systems.

Transcriptional response to prolonged perchlorate exposure in the methanogen Methanosarcina barkeri and implications for Martian habitability

Observations of trace methane (CH4) in the Martian atmosphere are significant to the astrobiology community given the overwhelming contribution of biological methanogenesis to atmospheric CH4 on Earth. Previous studies have shown that methanogenic Archaea can generate CH4 when incubated with perchlorates, highly oxidizing chaotropic salts which have been found across the Martian surface. However, the regulatory mechanisms behind this remain completely unexplored. In this study we performed comparative transcriptomics on the methanogen Methanosarcina barkeri, which was incubated at 30˚C and 0˚C with 10-20 mM calcium-, magnesium-, or sodium perchlorate. Consistent with prior studies, we observed decreased CH4 production and apparent perchlorate reduction, with the latter process proceeding by heretofore essentially unknown mechanisms. Transcriptomic responses of M. barkeri to perchlorates include up-regulation of osmoprotectant transporters and selection against redox-sensitive amino acids. Increased expression of methylamine methanogenesis genes suggest competition for H2 with perchlorate reduction, which we propose is catalyzed by up-regulated molybdenum-containing enzymes and maintained by siphoning diffused H2 from energy-conserving hydrogenases. Methanogenesis regulatory patterns suggest Mars' freezing temperatures alone pose greater constraints to CH4 production than perchlorates. These findings increase our understanding of methanogen survival in extreme environments and confers continued consideration of a potential biological contribution to Martian CH4.

Extracellular electron uptake in Methanosarcinales is independent of multiheme c-type cytochromes

The co-occurrence of Geobacter and Methanosarcinales is often used as a proxy for the manifestation of direct interspecies electron transfer (DIET) in the environment. Here we tested eleven new co-culture combinations between methanogens and electrogens. Previously, only the most electrogenic Geobacter paired by DIET with Methanosarcinales methanogens, namely G. metallireducens and G. hydrogenophilus. Here we provide additional support, and show that five additional Methanosarcinales paired with G. metallireducens, while a strict hydrogenotroph could not. We also show that G. hydrogenophilus, which is incapable to grow with a strict hydrogenotrophic methanogen, could pair with a strict non-hydrogenotrophic Methanosarcinales. Likewise, an electrogen outside the Geobacter cluster (Rhodoferrax ferrireducens) paired with Methanosarcinales but not with strict hydrogenotrophic methanogens. The ability to interact with electrogens appears to be conserved among Methanosarcinales, the only methanogens with c-type cytochromes, including multihemes (MHC). Nonetheless, MHC, which are often linked to extracellular electron transfer, were neither unique nor universal to Methanosarcinales and only two of seven Methanosarcinales tested had MHC. Of these two, one strain had an MHC-deletion knockout available, which we hereby show is still capable to retrieve extracellular electrons from G. metallireducens or an electrode suggesting an MHC-independent strategy for extracellular electron uptake.

Archaeal Cell Walls

The cell wall of archaea, as of any other prokaryote, is surrounding the cell outside the cytoplasmic membrane and is mediating the interaction with the environment. In this regard, it can be involved in cell shape maintenance, protection against virus, heat, acidity or alkalinity. Throughout the formation of pore like structures, it can resemble a micro sieve and thereby enable or disable transport processes. In some cases, cell wall components can make up more than 10% of the whole cellular protein. So far, a great variety of different cell envelope structures and compounds have be found and described in detail. From all archaeal cell walls described so far, the most common structure is the S-layer. Other archaeal cell wall structures are pseudomurein, methanochondroitin, glutaminylglycan, sulfated heteropolysaccharides and protein sheaths and they are sometimes associated with additional proteins and protein complexes like the STABLE protease or the bindosome. Recent advances in electron microscopy also illustrated the presence of an outer(most) cellular membrane within several archaeal groups, comparable to the Gram-negative cell wall within bacteria. Each new cell wall structure that can be investigated in detail and that can be assigned with a specific function helps us to understand, how the earliest cells on earth might have looked like.

Archaeal S-Layers: Overview and Current State of the Art

In contrast to bacteria, all archaea possess cell walls lacking peptidoglycan and a number of different cell envelope components have also been described. A paracrystalline protein surface layer, commonly referred to as S-layer, is present in nearly all archaea described to date. S-layers are composed of only one or two proteins and form different lattice structures. In this review, we summarize current understanding of archaeal S-layer proteins, discussing topics such as structure, lattice type distribution among archaeal phyla and glycosylation. The hexagonal lattice type is dominant within the phylum Euryarchaeota, while in the Crenarchaeota this feature is mainly associated with specific orders. S-layers exclusive to the Crenarchaeota have also been described, which are composed of two proteins. Information regarding S-layers in the remaining archaeal phyla is limited, mainly due to organism description through only culture-independent methods. Despite the numerous applied studies using bacterial S-layers, few reports have employed archaea as a study model. As such, archaeal S-layers represent an area for exploration in both basic and applied research.

The acid soluble extracellular polymeric substance of aerobic granular sludge dominated by Defluviicoccus sp

A new acid soluble extracellular polymeric substance (acid soluble EPS) was extracted from an acetate fed aerobic granular sludge reactor operated at 35 °C. Acid soluble EPS dominated granules exhibited a remarkable and distinctive tangled tubular morphology. These granules are dominated by Defluviicoccus Cluster II organisms. Acetic acid instead of the usually required alkaline extraction medium was needed to dissolve the granules and solubilise the polymeric matrix. The extracted acid soluble EPS was analysed and identified using various instrumental analysis including ¹H and ¹³C Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy and Raman spectroscopy. In addition, the glycoconjugates were characterized by fluorescence lectin-binding analysis. The acid soluble EPS is α-(1 → 4) linked polysaccharide, containing both glucose and galactose as monomers. There are OCH₃ groups connected to the glucose monomer. Transmission and scanning electron microscopy (TEM, SEM) as well as confocal laser scanning microscopy (CLSM) showed that the acid soluble EPS was present as a tightly bound capsular EPS around bacterial cells ordered into a sarcinae-like growth pattern. The special granule morphology is decided by the acid soluble EPS produced by Defluviicoccus Cluster II organisms. This work shows that no single one method can be used to extract all possible extracellular polymeric substances. Results obtained here can support the elucidation of biofilm formation and structure in future research.

Mechanical and cell-to-cell adhesive properties of aggregated Methanosarcina

The mechanical and adhesive properties as well as the turgor pressure of microbes play an important role in cell growth and aggregation. By applying AFM together with finite element modelling, one can determine the cell wall structural homogeneity, mechanical and cell-to-cell adhesive properties for aggregated Methanosarcina barkeri cells. This also allows a novel approach to determine in-aggregate turgor pressure determination. Analyzing the AFM force-indentation response of the aggregates under loads less than 10 nN, our study reveals structural inhomogeneity of the polymeric part of the cell wall material and suggests that the cell wall consists of two layers of methanochondroitin (external: with a thickness of 3 ± 1 nm and internal: with a thickness of 169 ± 30 nm). On average, the hyperelastic finite element model showed that the internal layer is more rigid (μ = 14 ± 4 MPa) than the external layer (μ = 2.8 ± 0.9 MPa). To determine the turgor pressure and adhesiveness of the cells, a specific mode of indentation (under a load of 45 nN), aimed towards the centre of the individual aggregate, was performed. By modelling the AFM induced decohesion of the aggregate, the turgor pressure and the cell-to-cell adhesive interface properties could be determined. On average, the turgor pressure is estimated to be 59 ± 22 kPa, the interface strength is 78 ± 12 kPa and the polymer network extensibility is 2.8 ± 0.9 nm. We predict that internal cell wall comprised highly compressed methanochondroitin chains and we are able to identify a conceptual model for stress dependent inner cell wall growth.

S-layer and cytoplasmic membrane - exceptions from the typical archaeal cell wall with a focus on double membranes

The common idea of typical cell wall architecture in archaea consists of a pseudo-crystalline proteinaceous surface layer (S-layer), situated upon the cytoplasmic membrane. This is true for the majority of described archaea, hitherto. Within the crenarchaea, the S-layer often represents the only cell wall component, but there are various exceptions from this wall architecture. Beside (glycosylated) S-layers in (hyper)thermophilic cren- and euryarchaea as well as halophilic archaea, one can find a great variety of other cell wall structures like proteoglycan-like S-layers (Halobacteria), glutaminylglycan (Natronococci), methanochondroitin (Methanosarcina) or double layered cell walls with pseudomurein (Methanothermus and Methanopyrus). The presence of an outermost cellular membrane in the crenarchaeal species Ignicoccus hospitalis already gave indications for an outer membrane similar to Gram-negative bacteria. Although there is just limited data concerning their biochemistry and ultrastructure, recent studies on the euryarchaeal methanogen Methanomassiliicoccus luminyensis, cells of the ARMAN group, and the SM1 euryarchaeon delivered further examples for this exceptional cell envelope type consisting of two membranes.

S-layer, surface-accessible, and concanavalin A binding proteins of Methanosarcina acetivorans and Methanosarcina mazei

The outermost cell envelope structure of many archaea and bacteria contains a proteinaceous lattice termed the surface layer or S-layer. It is typically composed of only one or two abundant, often posttranslationally modified proteins that self-assemble to form the highly organized arrays. Surprisingly, over 100 proteins were annotated to be S-layer components in the archaeal species Methanosarcina acetivorans C2A and Methanosarcina mazei Gö1, reflecting limitations of current predictions. An in vivo biotinylation methodology was devised to affinity tag surface-exposed proteins while overcoming unique challenges in working with these fragile organisms. Cells were adapted to growth under N2 fixing conditions, thus, minimizing free amines reactive to the NHS-label, and high pH media compatible with the acylation chemistry was used. A 3-phase separation procedure was employed to isolate intact, labeled cells from lysed-cell derived proteins. Streptavidin affinity enrichment followed by stringent wash conditions removed nonspecifically bound proteins. This methodology revealed S-layer proteins in M. acetivorans C2A and M. mazei Gö1 to be MA0829 and MM1976, respectively. Each was demonstrated to exist as multiple glycosylated forms using SDS-PAGE coupled with glycoprotein-specific staining, and by interaction with the lectin, Concanavalin A. A number of additional surface-exposed proteins and glycoproteins were identified and included all three subunits of the thermosome: the latter suggests that the chaperonin complex is both surface- and cytoplasmically localized. This approach provides an alternative strategy to study surface proteins in the archaea.

The Methanosarcina barkeri genome: comparative analysis with Methanosarcina acetivorans and Methanosarcina mazei reveals extensive rearrangement within methanosarcinal genomes

We report here a comparative analysis of the genome sequence of Methanosarcina barkeri with those of Methanosarcina acetivorans and Methanosarcina mazei. The genome of M. barkeri is distinguished by having an organization that is well conserved with respect to the other Methanosarcina spp. in the region proximal to the origin of replication, with interspecies gene similarities as high as 95%. However, it is disordered and marked by increased transposase frequency and decreased gene synteny and gene density in the distal semigenome. Of the 3,680 open reading frames (ORFs) in M. barkeri, 746 had homologs with better than 80% identity to both M. acetivorans and M. mazei, while 128 nonhypothetical ORFs were unique (nonorthologous) among these species, including a complete formate dehydrogenase operon, genes required for N-acetylmuramic acid synthesis, a 14-gene gas vesicle cluster, and a bacterial-like P450-specific ferredoxin reductase cluster not previously observed or characterized for this genus. A cryptic 36-kbp plasmid sequence that contains an orc1 gene flanked by a presumptive origin of replication consisting of 38 tandem repeats of a 143-nucleotide motif was detected in M. barkeri. Three-way comparison of these genomes reveals differing mechanisms for the accrual of changes. Elongation of the relatively large M. acetivorans genome is the result of uniformly distributed multiple gene scale insertions and duplications, while the M. barkeri genome is characterized by localized inversions associated with the loss of gene content. In contrast, the short M. mazei genome most closely approximates the putative ancestral organizational state of these species.

Primary structure of selected archaeal mesophilic and extremely thermophilic outer surface layer proteins

The archaea are recognized as a separate third domain of life together with the bacteria and eucarya. The archaea include the methanogens, extreme halophiles, thermoplasmas, sulfate reducers and sulfur metabolizing thermophiles, which thrive in different habitats such as anaerobic niches, salt lakes, and marine hydrothermals systems and continental solfataras. Many of these habitats represent extreme environments in respect to temperature, osmotic pressure and pH-values and remind on the conditions of the early earth. The cell envelope structures were one of the first biochemical characteristics of archaea studied in detail. The most common archaeal cell envelope is composed of a single crystalline protein or glycoprotein surface layer (S-layer), which is associated with the outside of the cytoplasmic membrane. The S-layers are directly exposed to the extreme environment and can not be stabilized by cellular components. Therefore, from comparative studies of mesophilic and extremely thermophilic S-layer proteins hints can be obtained about the molecular mechanisms of protein stabilization at high temperatures. First crystallization experiments of surface layer proteins under microgravity conditions were successful. Here, we report on the biochemical features of selected mesophilic and extremely archaeal S-layer (glyco-) proteins.

A comprehensive study into the molecular methodology and molecular biology of methanogenic Archaea

Methanogens belong to the kingdom of Euryarchaeota in the domain of Archaea. The Archaea differ from Bacteria in many aspects important to molecular work. Among these are cell wall composition, their sensitivity to antibiotics, their translation and transcription machinery, and their very strict demands to anaerobic culture conditions. These differences may, at least partly, be responsible for the delay in availability of genetic research tools for methanogens. At present, however, the research within genetics of methanogens and their gene regulation and expression is in rapid progress. Two complete methanogenic genomes have been sequenced and published and more are underway. Besides, sequences are known from a multitude of individual genes from methanogens. Standard methods for simple DNA and RNA work can normally be employed, but permeabilization of the cell wall may demand special procedures. Efficient genetic manipulation systems, including shuttle and integration vector systems, have appeared for mesophilic, but not for thermophilic species within the last few years and will have a major impact on future investigations of methanogenic molecular biology.

Archaebacterial phylogeny: perspectives on the urkingdoms

Comparisons of complete 16S ribosomal RNA sequences have been used to confirm, refine and extend earlier concepts of archaebacterial phylogeny. The archaebacteria fall naturally into two major branches or divisions, I--the sulfur-dependent thermophilic archaebacteria, and II--the methanogenic archaebacteria and their relatives. Division I comprises a relatively closely related and phenotypically homogeneous collection of thermophilic sulfur-dependent species--encompassing the genera Sulfolobus, Thermoproteus, Pyrodictium and Desulfurococcus. The organisms of Division II, however, form a less compact grouping phylogenetically, and are also more diverse in phenotype. All three of the (major) methanogen groups are found in Division II, as are the extreme halophiles and two types of thermoacidophiles, Thermoplasma acidophilum and Thermococcus celer. This last species branches sufficiently deeply in the Division II line that it might be considered to represent a separate, third Division. However, both the extreme halophiles and Tp. acidophilum branch within the cluster of methanogens. The extreme halophiles are specifically related to the Methanomicrobiales, to the exclusion of both the Methanococcales and the Methanobacteriales. Tp. acidophilum is peripherally related to the halophile-Methanomicrobiales group. By 16S rRNA sequence measure the archaebacteria constitute a phylogenetically coherent grouping (clade), which excludes both the eubacteria and the eukaryotes--a conclusion that is supported by other sequence evidence as well. Alternative proposals for archaebacterial phylogeny, not based upon sequence evidence, are discussed and evaluated. In particular, proposals to rename (reclassify) various subgroups of the archaebacteria as new kingdoms are found wanting, for both their lack of proper experimental support and the taxonomic confusion they introduce.

In situ reverse transcription-PCR for monitoring gene expression in individual Methanosarcina mazei S-6 cells

An in situ reverse transcription-PCR protocol for detecting specific mRNA in Methanosarcina mazei S-6 is described. This method allowed us to detect heat shock-induced increases in the intracellular levels of the transcript of the universal stress gene dnaK. The cell walls of paraformaldehyde-fixed cells were permeabilized by a thermal cycling procedure or by lysozyme treatment, and the cellular DNA was removed with DNase. The cells were subjected to a seminested reverse transcription-PCR protocol in which a digoxigenin-labeled primer was used. Detection of the reporter molecule was based on the 2-hydroxy-3-naphtoic acid-2'-phenylanilide phosphate-Fast Red detection system and binding of anti-digoxigenin-alkaline phosphatase conjugate. Fluorescence in permeabilized cells increased after a heat shock compared to fluorescence in non-heat-shocked cells, and the increase corresponded to an increase in the level of the dnaK transcript.

The structure of the exopolysaccharide produced by the halophilic Archaeon Haloferax mediterranei strain R4 (ATCC 33500)

The halophilic Archaeon Haloferax mediterranei exudes into the growth medium a high molecular weight sulfated polysaccharide. The structure of the repeating unit of this polymer was determined by a combination of glycose, methylation, and sulfate analysis, periodate oxidation, and 1D and 2D NMR spectroscopic analysis of the native and periodate-oxidised/reduced polysaccharides. The location of the sulfate group was established from the 1H and 13C NMR data. The structure of the repeating unit of the polysaccharide may be written as [formula: see text]

Archaeal grpE: transcription in two different morphologic stages of Methanosarcina mazei and comparison with dnaK and dnaJ

Transcription of the heat shock gene grpE was studied in two different morphologic stages of the archaeon Methanosarcina mazei S-6 that differ in resistance to physical and chemical traumas: single cells and packets. While single cells are directly exposed to environmental changes, such as temperature elevations, cells in packets are surrounded by intercellular and peripheral material that keeps them together in a globular structure which can reach several millimeters in diameter. grpE transcript levels determined by Northern (RNA) blotting peaked after a 15-min heat shock in single cells. In contrast, the highest transcript levels in packets were observed after the longest heat shock tested, 60 min. The same response profiles were demonstrated by primer extension experiments and S1 nuclease analysis. A comparison of the grpE response to heat shock with those of dnaK and dnaJ showed that the grpE transcript level was the most increased, closely followed by that of the dnaK transcript, with that of the dnaJ gene being the least augmented. Transcription of grpE started at the same site under normal and heat shock temperatures, and the transcript was consistently approximately 700 bases long. Codon usage patterns revealed that the three archaeal genes use most codons and have the same codon preference for 61% of the amino acids.

Immunochemistry and localization of the enzyme disaggregatase in Methanosarcina mazei

The enzyme disaggregatase (Dag) from Methanosarcina mazei was studied immunochemically. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified Dag under reducing and nonreducing conditions revealed a single band with a 94-kDa molecular mass. Dag was found to be immunogenic in rabbits; a polyclonal antibody probe was prepared and used to detect the enzyme by slide immunoenzymatic assay, immunofluorescence, and immunoblotting in various species of Methanosarcina known to convert from packets to single cells, including M. mazei. The enzyme could not be detected in other members of the family Methanosarcinaceae that do not convert. By immunogold electron microscopy, Dag was mapped to the cell wall of packets and to the cell membrane of single cells of two M. mazei strains.

Structural features of archaebacterial cell envelopes

Regularly arrayed surface (glyco) proteins--often referred to as S layers--are a common feature of the cell envelopes of almost all archaebacteria. We have selected some examples (Halobacterium, Sulfolobus, Thermoproteus, Pyrobaculum, Staphylothermus), and we describe the structure of their surface layers as revealed primarily by electron crystallography. In spite of a considerable diversity in shapes and dimensions, some common structural features emerge from the comparison. The glycoprotein arrays are composed of oligomeric units which are anchored in the plasma membrane; extended spacer or linker domains maintain the bulk of the more or less porous surface layers at a constant distance above the membrane surface, thus creating a quasi-periplasmic compartment. Functions ascribed to surface layers, such as compartmentalization, shape maintenance and determination, and adhesion are discussed.

Lamina, a novel multicellular form of Methanosarcina mazei S-6

A novel multicellular form of Methanosarcina mazei S-6 is described. It was termed lamina, and it formed during the exponential growth phase when packets or single cells were grown in 40 mM trimethylamine and a total concentration of 8.3 to 15.6 mM Ca2+ and/or Mg2+, in cultures that were not shaken. A distinct molecular event represented by the increment in expression and a spatial redistribution of an antigen during lamina formation is documented.

Nucleotide-activated oligosaccharides are intermediates of the cell wall polysaccharide of Methanosarcina barkeri

The cell wall of Methanosarcina barkeri consists of a heteropolysaccharide (methanochondroitin), which resembles the eukaryotic chondroitin. From cell extracts of Methanosarcina barkeri four uridine diphosphate and one undecaprenyl pyrophosphate-activated intermediate(s) of the methanochondroitin were isolated. In contrast to the known biosynthetic pathways of polysaccharides from other prokaryotes and eukaryotes, nucleotide activated oligosaccharide precursors are involved in the case of the methanochondroitin. Usually, oligosaccharides are synthesized at the lipid stage.

Isolation and characterization of disaggregatase from Methanosarcina mazei LYC

At certain stages in its growth cycle, Methanosarcina mazei produces an enzyme (disaggregatase) that causes aggregates to separate into single cells. M. mazei S-6 and LYC both produce this enzymatic activity, although the specificities of activities differ. The disaggregatase of M. mazei S-6 had little effect on strain LYC cells, but the disaggregatase of M. mazei LYC disaggregated both strain LYC and strain S-6 cells. The disaggregatase of M. mazei LYC was purified by column chromatography, and it apparently consisted of two similar subunits with a combined molecular size of about 180,000 Da. Strain S-6 culture supernatants contained 14 U of activity per liter when activity was measured as uronic acids released from purified cell wall material. When the activity was quantified as the release of uronic acids from boiled M. mazei S-6 cells, the highest activity was found at pH 4.7 and at 35 degrees C.

Enzyme-Linked Immunosorbent Assays for the Specific and Sensitive Quantification of Methanosarcina mazei and Methanobacterium bryantii

Three microtitration plate enzyme-linked immunosorbent assays (ELISAs) have been developed: a competitive ELISA and a two-site (or indirect sandwich) ELISA for Methanosarcina mazei S6 and a two-site ELISA for Methanobacterium bryantii FR-2. The assays were sensitive, with limits of cell protein detection of 3 ng ml −1 , 5 ng ml −1 , and 50 ng ml −1 , respectively, and showed good precision. The M. mazei assays used monoclonal antibodies and were entirely species specific, showing no cross-reaction with methanogens of other genera or with other species of the same genus. The Methanobacterium bryantii assay, which used two polyclonal antisera, showed only a slight cross-reaction with one other Methanobacterium species but no cross-reaction with methanogens of other genera. The use of the ELISAs for quantitative analysis of mixed cultures and of sewage sludge samples was investigated. Sludge diluted at 1:10 3 or more caused no significant interference in any of the three ELISAs. Various cultures of bacteria, methanogens, and nonmethanogens at a protein concentration of 50 μg ml −1 showed no significant interference in the M. mazei competitive assay and the Methanobacterium bryantii two-site assay, although they did cause falsely low results in the M. mazei two-site assay.

Adaptation for growth at various saline concentrations by the archaebacterium Methanosarcina thermophila

We report the ability of Methanosarcina thermophila TM-1 to adapt and grow in media containing NaCl concentrations of 0.005 to 1.2 M. When adapted to marine NaCl concentrations, this species ceased to produce the heteropolysaccharide outer layer typically formed by species of nonmarine origin. concomitant with this adaptation, M. thermophila ceased to grow as multicellular aggregates and existed solely in single-cell form. The sodium ion concentration was critical for the adaptation process, although magnesium ion appeared to contribute to the cell wall stability of single cells. The results suggest that these archaebacteria possess regulatory systems that enable them to adapt to environments with a wide range of saline concentrations.

Purification and use of Methanobacterium wolfei pseudomurein endopeptidase for lysis of Methanobacterium thermoautotrophicum

The pseudomurein-degrading enzyme from autolysates of Methanobacterium wolfei was purified approximately 500-fold to electrophoretic homogeneity by ion-exchange chromatography under anaerobic conditions. Analysis of the soluble cell wall fragments produced by the pure enzyme from a cell wall preparation of M. thermoautotrophicum indicated that it is a peptidase hydrolyzing the epsilon-Ala-Lys bond of pseudomurein. A partially purified preparation of pseudomurein endopeptidase was free of nuclease activity and thus proved useful for the preparation in high yields of undegraded chromosomal and plasmid DNA from M. thermoautotrophicum. The partially purified enzyme was also used for the preparation of protoplasts, which were stabilized by 0.8 M sucrose. Under growth conditions the protoplasts produced methane and increased up to 100-fold in size, but failed to regenerate a cell wall.