Studies on some methane-utilizing bacteria

Advances and perspectives of using stable isotope probing (SIP)-based technologies in contaminant biodegradation

Stable isotope probing (SIP) is a powerful tool to study microbial community structure and function in both nature and engineered environments. Coupling with advanced genomics and other techniques, SIP studies have generated substantial information to allow researchers to draw a clearer picture of what is occurring in complex microbial ecosystems. This review provides an overview of the advances of SIP-based technologies over time, summarizes the status of SIP applications to contaminant biodegradation, provides critical perspectives on ecological interactions within the community, and important factors (controllable and non-controllable) to be considered in SIP experimental designs and data interpretation. Current trend and perspectives of adapting SIP techniques for environmental applications are also discussed.

Methylocystis iwaonis sp. nov., a type II methane-oxidizing bacterium from surface soil of a rice paddy field in Japan, and emended description of the genus Methylocystis (ex Whittenbury et al. 1970) Bowman et al. 1993

A novel methane-oxidizing bacterial strain SS37A-ReT was isolated from surface soil of a rice paddy field in Japan. Cells were Gram-stain-negative, motile rods with single polar flagellum and type II intracytoplasmic membrane arrangement. The strain grew on methane or methanol as the sole carbon and energy source. It grew at 15–37 °C (optimum 25–30 °C), pH 6.0–9.0 (optimum 7.0–8.0) and with 0–0.1 % (w/w) NaCl (no growth at 0.5 % or above). Cells formed cysts, but not exospores. The results of sequence analysis of the 16S rRNA gene indicated that SS37A-ReT represented a member of the family Methylocystaceae , with the highest similarity (98.9 %) to Methylocystis parva corrig. OBBPT. Phylogenetic analysis of pmoA and mxaF genes and core genes in the genome indicated that the strain was closely related to the members of the genus Methylocystis , while the analysis of the mmoX gene indicated the close relationships with the genus Methylosinus . The values of genome relatedness between SS37A-ReT and species of the genera Methylocystis and Methylosinus were 78.6–82.5% and 21.7–24.9 % estimated by the average nucleotide identity and digital DNA–DNA hybridisation, respectively, showing the highest values with Methylocystis echinoides LMG 27198T. The DNA G+C content was 63.2 mol% (genome). The major quinone and fatty acids were Q-8 and, C18 : 1 (C18 : 1ω8t and C18 : 1ω8c) and C18 : 2, respectively. On the basis of the phenotypic and phylogenetic features, the strain represents a novel species of the genus Methylocystis , for which the name Methylocystis iwaonis sp. nov. is proposed. The type strain is SS37A-ReT (=JCM 34278T =NBRC 114996T=KCTC 82710T).

Comparative genomics reveals electron transfer and syntrophic mechanisms differentiating methanotrophic and methanogenic archaea

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate-reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure culture. Here, we reconstruct 28 ANME genomes from environmental metagenomes and flow sorted syntrophic consortia. Together with a reanalysis of previously published datasets, these genomes enable a comparative analysis of all marine ANME clades. We review the genomic features that separate ANME from their methanogenic relatives and identify what differentiates ANME clades. Large multiheme cytochromes and bioenergetic complexes predicted to be involved in novel electron bifurcation reactions are well distributed and conserved in the ANME archaea, while significant variations in the anabolic C1 pathways exists between clades. Our analysis raises the possibility that methylotrophic methanogenesis may have evolved from a methanotrophic ancestor.

A comparative genomics study of anaerobic methanotrophic (ANME) archaea reveals the genetic "parts list" associated with the repeated evolutionary transition between methanogenic and methanotrophic metabolism in the archaeal domain of life.

From Biogas and Hydrogen to Microbial Protein Through Co-Cultivation of Methane and Hydrogen Oxidizing Bacteria

Increasing efforts are directed towards the development of sustainable alternative protein sources among which microbial protein (MP) is one of the most promising. Especially when waste streams are used as substrates, the case for MP could become environmentally favorable. The risks of using organic waste streams for MP production-the presence of pathogens or toxicants-can be mitigated by their anaerobic digestion and subsequent aerobic assimilation of the (filter-sterilized) biogas. Even though methane and hydrogen oxidizing bacteria (MOB and HOB) have been intensively studied for MP production, the potential benefits of their co-cultivation remain elusive. Here, we isolated a diverse group of novel HOB (that were capable of autotrophic metabolism), and co-cultured them with a defined set of MOB, which could be grown on a mixture of biogas and H2/O2. The combination of MOB and HOB, apart from the CH4 and CO2 contained in biogas, can also enable the valorization of the CO2 that results from the oxidation of methane by the MOB. Different MOB and HOB combinations were grown in serum vials to identify the best-performing ones. We observed synergistic effects on growth for several combinations, and in all combinations a co-culture consisting out of both HOB and MOB could be maintained during five days of cultivation. Relative to the axenic growth, five out of the ten co-cultures exhibited 1.1-3.8 times higher protein concentration and two combinations presented 2.4-6.1 times higher essential amino acid content. The MP produced in this study generally contained lower amounts of the essential amino acids histidine, lysine and threonine, compared to tofu and fishmeal. The most promising combination in terms of protein concentration and essential amino acid profile was Methyloparacoccus murrelli LMG 27482 with Cupriavidus necator LMG 1201. Microbial protein from M. murrelli and C. necator requires 27-67% less quantity than chicken, whole egg and tofu, while it only requires 15% more quantity than the amino acid-dense soybean to cover the needs of an average adult. In conclusion, while limitations still exist, the co-cultivation of MOB and HOB creates an alternative route for MP production leveraging safe and sustainably-produced gaseous substrates.

Isolation and characterisation of Methylocystis spp. for poly-3-hydroxybutyrate production using waste methane feedstocks

Waste plastic and methane emissions are two anthropogenic by-products exacerbating environmental pollution. Methane-oxidizing bacteria (methanotrophs) hold the key to solving these problems simultaneously by utilising otherwise wasted methane gas as carbon source and accumulating the carbon as poly-3-hydroxybutyrate, a biodegradable plastic polymer. Here we present the isolation and characterisation of two novel Methylocystis strains with the ability to produce up to 55.7 ± 1.9% poly-3-hydroxybutyrate of cell dry weight when grown on methane from different waste sources such as landfill and anaerobic digester gas. Methylocystis rosea BRCS1 isolated from a recreational lake and Methylocystis parvus BRCS2 isolated from a bog were whole genome sequenced using PacBio and Illumina genome sequencing technologies. In addition to potassium nitrate, these strains were also shown to grow on ammonium chloride, glutamine and ornithine as nitrogen source. Growth of Methylocystis parvus BRCS2 on Nitrate Mineral Salt (NMS) media with 0.1% methanol vapor as carbon source was demonstrated. The genetic tractability by conjugation was also determined with conjugation efficiencies up to 2.8 × 10^–2 and 1.8 × 10^–2 for Methylocystis rosea BRCS1 and Methylocystis parvus BRCS2 respectively using a plasmid with ColE1 origin of replication. Finally, we show that Methylocystis species can produce considerable amounts of poly-3-hydroxybutyrate on waste methane sources without impaired growth, a proof of concept which opens doors to their use in integrated bio-facilities like landfills and anaerobic digesters.

Methanobactin and the Link between Copper and Bacterial Methane Oxidation

Methanobactins (mbs) are low-molecular-mass (<1,200 Da) copper-binding peptides, or chalkophores, produced by many methane-oxidizing bacteria (methanotrophs). These molecules exhibit similarities to certain iron-binding siderophores but are expressed and secreted in response to copper limitation. Structurally, mbs are characterized by a pair of heterocyclic rings with associated thioamide groups that form the copper coordination site. One of the rings is always an oxazolone and the second ring an oxazolone, an imidazolone, or a pyrazinedione moiety. The mb molecule originates from a peptide precursor that undergoes a series of posttranslational modifications, including (i) ring formation, (ii) cleavage of a leader peptide sequence, and (iii) in some cases, addition of a sulfate group. Functionally, mbs represent the extracellular component of a copper acquisition system. Consistent with this role in copper acquisition, mbs have a high affinity for copper ions. Following binding, mbs rapidly reduce Cu(2+) to Cu(1+). In addition to binding copper, mbs will bind most transition metals and near-transition metals and protect the host methanotroph as well as other bacteria from toxic metals. Several other physiological functions have been assigned to mbs, based primarily on their redox and metal-binding properties. In this review, we examine the current state of knowledge of this novel type of metal-binding peptide. We also explore its potential applications, how mbs may alter the bioavailability of multiple metals, and the many roles mbs may play in the physiology of methanotrophs.

Methylomagnum ishizawai gen. nov., sp. nov., a mesophilic type I methanotroph isolated from rice rhizosphere

An aerobic, methane-oxidizing bacterium (strain RS11D-PrT) was isolated from rice rhizosphere. Cells of strain RS11D-PrT were Gram-stain-negative, motile rods with a single polar flagellum and contained an intracytoplasmic membrane system typical of type I methanotrophs. The strain utilized methane and methanol as sole carbon and energy sources. It could grow at 20–37 °C (optimum 31–33 °C), at pH 6.8–7.4 (range 5.5–9.0) and with 0–0.2 % (w/v) NaCl (there was no growth at above 0.5 % NaCl). pmoA and mmoX genes were present. The ribulose monophosphate and/or ribulose bisphosphate pathways were used for carbon assimilation. Results of sequence analysis of 16S rRNA genes showed that strain RS11D-PrT is related closely to the genera Methylococcus, Methylocaldum, Methyloparacoccus and Methylogaea in the family Methylococcaceae. The similarity was low (94.6 %) between strain RS11D-PrT and the most closely related type strain (Methyloparacoccus murrellii R-49797T). The DNA G+C content was 64.1 mol%. Results of phylogenetic analysis of the pmoA gene and chemotaxonomic data regarding the major cellular fatty acids (C16 : 1ω7c, C16 : 0 and C14 : 0) and the major respiratory quinone (MQ-8) also indicated the affiliation of strain RS11D-PrT to the Methylococcus–Methylocaldum–Methyloparacoccus–Methylogaea clade. On the basis of phenotypic, genotypic and phylogenetic characteristics, strain RS11D-PrT is considered to represent a novel genus and species within the family Methylococcaceae, for which the name Methylomagnum ishizawai gen. nov., sp. nov. is proposed. The type strain is RS11D-PrT ( = JCM 18894T = NBRC 109438T = DSM 29768T = KCTC 4681T).

Current trends in trichloroethylene biodegradation: a review

Over the past few years biodegradation of trichloroethylene (TCE) using different microorganisms has been investigated by several researchers. In this review article, an attempt has been made to present a critical summary of the recent results related to two major processes--reductive dechlorination and aerobic co-metabolism used for TCE biodegradation. It has been shown that mainly Clostridium sp. DC-1, KYT-1, Dehalobacter, Dehalococcoides, Desulfuromonas, Desulfitobacterium, Propionibacterium sp. HK-1, and Sulfurospirillum bacterial communities are responsible for the reductive dechlorination of TCE. Efficacy of bacterial communities like Nitrosomonas, Pseudomonas, Rhodococcus, and Xanthobacter sp. etc. for TCE biodegradation under aerobic conditions has also been examined. Mixed cultures of diazotrophs and methanotrophs have been used for TCE degradation in batch and continuous cultures (biofilter) under aerobic conditions. In addition, some fungi (Trametes versicolor, Phanerochaete chrysosporium ME-446) and Actinomycetes have also been used for aerobic biodegradation of TCE. The available information on kinetics of biofiltration of TCE and its degradation end-products such as CO2 are discussed along with the available results on the diversity of bacterial community obtained using molecular biological approaches. It has emerged that there is a need to use metabolic engineering and molecular biological tools more intensively to improve the robustness of TCE degrading microbial species and assess their diversity.

Diversity of cultivable methane-oxidizing bacteria in microsites of a rice paddy field: investigation by cultivation method and fluorescence in situ hybridization (FISH)

The diversity of cultivable methane-oxidizing bacteria (MOB) in the rice paddy field ecosystem was investigated by combined culture-dependent and fluorescence in situ hybridization (FISH) techniques. Seven microsites of a Japanese rice paddy field were the focus of the study: floodwater, surface soil, bulk soil, rhizosphere soil, root, basal stem of rice plant, and rice stumps of previous harvest. Based on pmoA gene analysis and transmission electron microscopy (TEM), four type I, and nine type II MOB isolates were obtained from the highest dilution series of enrichment cultures. The type I MOB isolates included a novel species in the genus Methylomonas from floodwater and this is the first type I MOB strain isolated from floodwater of a rice paddy field. In the type I MOB, two isolates from stumps were closely related to Methylomonas spp.; one isolate obtained from rhizosphere soil was most related to Methyloccocus-Methylocaldum-Methylogaea clade. Almost all the type II MOB isolates were related to Methylocystis methanotrophs. FISH confirmed the presence of both types I and II MOB in all the microsites and in the related enrichment cultures. The study reported, for the first time, the diversity of cultivable methanotrophs including a novel species of type I MOB in rice paddy field compartments. Refining growth media and culture conditions, in combination with molecular approaches, will allow us to broaden our knowledge on the MOB community in the rice paddy field ecosystem and consequently to implement strategies for mitigating CH₄ emission from this ecosystem.

Methylomonas koyamae sp. nov., a type I methane-oxidizing bacterium from floodwater of a rice paddy field

A novel methane-oxidizing bacterium, strain Fw12E-Y(T), was isolated from floodwater of a rice paddy field in Japan. Cells of strain Fw12E-Y(T) were Gram-negative, motile rods with a single polar flagellum and type I intracytoplasmic membrane arrangement. The strain grew only on methane or methanol as sole carbon and energy source. It was able to grow at 10-40 °C (optimum 30 °C), at pH 5.5-7.0 (optimum 6.5) and with 0-0.1% (w/w) NaCl (no growth above 0.5% NaCl). 16S rRNA gene sequence analysis showed that strain Fw12E-Y(T) is related most closely to members of the genus Methylomonas, but at low levels of similarity (95.0-95.4%). Phylogenetic analysis of pmoA and mxaF genes indicated that the strain belongs to the genus Methylomonas (97 and 92 % deduced amino acid sequence identities to Methylomonas methanica S1(T), respectively). The DNA G+C content of strain Fw12E-Y(T) was 57.1 mol%. Chemotaxonomic data regarding the major quinone (MQ-8) and major fatty acids (C(16:1) and C(14:0)) also supported its affiliation to the genus Methylomonas. Based on phenotypic, genomic and phylogenetic data, strain Fw12E-Y(T) is considered to represent a novel species of the genus Methylomonas, for which the name Methylomonas koyamae sp. nov. is proposed. The type strain is Fw12E-Y(T) ( = JCM 16701(T) = NBRC 105905(T) = NCIMB 14606(T)).

Strain-specific incorporation of methanotrophic biomass into eukaryotic grazers in a rice field soil revealed by PLFA-SIP

In wetland ecosystems, methane is actively utilized by methanotrophs. The immobilized methane carbon is then passed on to other organisms such as grazers. Here, we traced the incorporation of methanotrophic biomass into eukaryotes in a rice field soil using phospholipid fatty acid stable-isotope probing (PLFA-SIP). Addition of (13)C-labeled cells of five methanotrophs to soil (5 × 10(7) cells g(-1) soil) did not affect the CO(2) release rate, but significantly increased the carbon isotopic ratio within 24 h. In 48 h, 2-7% of the added bacterial biomass carbon was detected as (13)CO(2) . The soil with Methylobacter luteus released the highest amount of (13)CO(2) , comparable to that with Escherichia coli. The amount of polyunsaturated PLFAs (C18:3ω6c and C20:4ω6c) was not affected by the addition of bacterial cells to soil, but their carbon isotopic ratio increased significantly within 24-48 h. The extent of (13)C-enrichment in PLFAs differed between the added methanotrophs, with the highest labeling upon addition of M. luteus. The relative abundance of (13) C-labeled C18:3ω6c to C20:4ω6C also differed between the strains. The results indicated that the eukaryotes in soil, probably protozoa, preferentially graze on specific methanotrophs and immediately incorporate their biomass.

Distribution of Methylomonas methanica and Methylosinus trichosporium in Cleveland Harbor as Determined by an Indirect Fluorescent Antibody-Membrane Filter Technique

An indirect fluorescent antibody-membrane filter staining technique, which permitted the autecological study of Methylomonas methanica and Methylosinus trichosporium, was developed. This technique was used to assay the numbers of these two organisms in Cleveland Harbor. The concentrations of M. methanica and M. trichosporium were found to be inversely proportional to the sampling depth, with the highest cell counts observed in the sediments. M. methanica was observed at every sampling station, whereas M. trichosporium was found at only two of the stations.

Microbial Oxidation of Hydrocarbons: Properties of a Soluble Methane Monooxygenase from a Facultative Methane-Utilizing Organism, Methylobacterium sp. Strain CRL-26

Methylobacterium sp. strain CRL-26 grown in a fermentor contained methane monooxygenase activity in soluble fractions. Soluble methane monooxygenase catalyzed the epoxidation/hydroxylation of a variety of hydrocarbons, including terminal alkenes, internal alkenes, substituted alkenes, branched-chain alkenes, alkanes (C(1) to C(8)), substituted alkanes, branched-chain alkanes, carbon monoxide, ethers, and cyclic and aromatic compounds. The optimum pH and temperature for the epoxidation of propylene by soluble methane monooxygenase were found to be 7.0 and 40 degrees C, respectively. Among various compounds tested, only NADH(2) or NADPH(2) could act as an electron donor. Formate and NAD (in the presence of formate dehydrogenase contained in the soluble fraction) or 2-butanol in the presence of NAD and secondary alcohol dehydrogenase generated the NADH(2) required for the methane monooxygenase. Epoxidation of propylene catalyzed by methane monooxygenase was not inhibited by a range of potential inhibitors, including metal-chelating compounds and potassium cyanide. Sulfhydryl agents and acriflavin inhibited monooxygenase activity. Soluble methane monooxygenase was resolved into three components by ion-exchange chromatography. All three compounds are required for the epoxidation and hydroxylation reactions.

Cell yields of bacteria grown on methane

Several mixed cultures of methane-oxidizing bacteria have been isolated. Among them, culture HR (consisting of two gram-negative rods, one 0.5 x 1.0 mu, the other 0.8 x 2 to 3 mu) was found to be the fastest-growing and to give the highest yields. Optimal conditions for rapid growth and high cell yields from methane were found to be: 30 C, NH(4) as nitrogen source, and pH 6.5. Requirements for CO(2) and Cu were observed. Under these conditions, generation times of approximately 3 hr and cell yields from methane between 65 and 70% could be attained. Culture HR can utilize methane, methanol, ethyl alcohol, 1-propanol, n-butyl alcohol, and glucose, but not propane, for growth. Yeast and beef extracts are inhibitory. Carbon balances demonstrate that few if any products other than cells and CO(2) are produced from methane under the growth conditions used. Cell analyses for carbon, hydrogen, nitrogen, and amino acid content of culture HR were also made.

Glyphosate-degrading microorganisms from industrial activated sludge

A plating medium was developed to isolate N-phosphonomethylglycine (glyphosate)-degrading microorganisms, with glyphosate as the sole phosphorus source. Two industrial biosystems treating glyphosate wastes contained elevated microbial counts on the medium. One purified isolate metabolized glyphosate to aminomethylphosphonic acid, mineralizing this accumulating intermediate during log growth. This microorganism has been identified as a Flavobacterium species.

Degradation of phenol and TCE using suspended and chitosan-bead immobilized Pseudomonas putida

The degradability of phenol and trichloroethene (TCE) by Pseudomonas putida BCRC 14349 in both suspended culture and immobilized culture systems are investigated. Chitosan beads at a size of about 1-2mm were employed to encapsulate the P. putida cells, becoming an immobilized culture system. The phenol concentration was controlled at 100 mg/L, and that of TCE was studied from 0.2 to 20 mg/L. The pH, between 6.7 and 10, did not affect the degradation of either phenol or TCE in the suspended culture system. However, it was found to be an important factor in the immobilized culture system in which the only significant degradation was observed at pH >8. This may be linked to the surface properties of the chitosan beads and its influence on the activity of the bacteria. The transfer yield of TCE on a phenol basis was almost the same for the suspended and immobilized cultures (0.032 mg TCE/mg phenol), except that these yields occurred at different TCE concentrations. The transfer yield at a higher TCE concentration for the immobilized system suggested that the cells immobilized in carriers can be protected from harsh environmental conditions. For kinetic rate interpretation, the Monod equation was employed to describe the degradation rates of phenol, while the Haldane's equation was used for TCE degradation. Based on the kinetic parameters obtained from the two equations, the rate for the immobilized culture systems was only about 1/6 to that of the suspended culture system for phenol degradation, and was about 1/2 for TCE degradation. The slower kinetics observed for the immobilized culture systems was probably due to the slow diffusion of substrate molecules into the beads. However, compared with the suspended cultures, the immobilized cultures may tolerate a higher TCE concentration as much less inhibition was observed and the transfer yield occurred at a higher TCE concentration.

Wide distribution of a novel pmoA-like gene copy among type II methanotrophs, and its expression in Methylocystis strain SC2

Experiments were conducted to determine if a novel pmoA-like gene (pmoA2) recently discovered in the methane-oxidizing bacterium Methylocystis strain SC2 (P. F. Dunfield, M. Tchawa Yimga, S. D. Dedysh, U. Berger, W. Liesack, and J. Heyer, FEMS Microbiol. Ecol. 41:17-26, 2002) is present in other methane-oxidizing bacteria (MOB), and if it is expressed. A newly developed primer combination (pmoA206f-pmoA703b) allowed a differential detection of pmoA1 and pmoA2. By using this primer combination, we identified pmoA2 in a wide range of type II MOB of the Methylosinus-Methylocystis group. However, screening by PCR and by Southern hybridization using a newly developed pmoA2-specific oligonucleotide probe also showed that closely related type II MOB, exhibiting 16S rRNA gene sequence identities of higher than 97%, may or may not harbor pmoA2. No pmoA2 was detected in five type I MOB tested: Methylococcus capsulatus strain Bath, Methylocaldum strain E10A, Methylobacter luteus, Methylomicrobium album, and Methylomonas strain D1a. In comparative sequence analyses, all pmoA2-like sequences formed a coherent cluster clearly distinct from pmoA1 sequences of type I and type II MOB, and from amoA sequences of the Nitrosomonas-Nitrosospira group. Phylogenetic analysis using the paml model suggested that pmoA2 is subject to strong purifying selection and therefore has an important cellular function. We probed total RNA extracts of Methylocystis strain SC2 for gene expression of pmoA. A strong signal was observed for pmoA1 in Northern hybridization, while the results obtained for pmoA2 were ambiguous. However, reverse transcription-PCR confirmed that pmoA2 was expressed, albeit at lower level than pmoA1. This provided experimental evidence that the gene product of pmoA2 may be a functionally active enzyme.

Biodegradation of N-phosphonomethyliminodiacetic acid by microorganisms from industrial activated sludge

A microbial population that biodegraded N-phosphonomethyliminodiacetic acid (PIA), a key component of glyphosate (N-phosphonomethylglycine) process waste, was established. The stoichiometric conversion of PIA to aminomethylphosphonic acid (AMPA) was observed in a laboratory sequencing batch reactor (SBR) containing activated sludge from a glyphosate-manufacturing facility and PIA as sole source of carbon. PIA degradation was determined by high-performance liquid chromatography and confirmed by radiolabeled studies. Greater than 90% of the [carboxymethyl-2-14C]-label of PIA was released as 14CO2 in 7 days using samples of sludge from the SBR. The cycle time required to biodegrade up to 7.5 mM PIA in SBRs was reduced from 21 to < 3 days. PIA biodegradation was also established in an immobilized bacteria column inoculated with mixed liquor from a SBR; > 99% PIA removal was achieved at an influent concentration of 2.2 mM and a hydraulic retention time of < 10 h. A pure bacterial culture was isolated from a SBR by streaking samples of sludge on solid media with PIA as sole carbon source. The isolate was identified as Xanthomonas maltophilia. In liquid culture, X. maltophilia degraded up to 4.4 mM PIA within 10 days and produced stoichiometric amounts of AMPA. The results demonstrate the biodegradation of PIA and suggest the potential for its treatment in industrial biological treatment systems.

IDENTITY OF THE PINK-PIGMENTED METHANOL-OXIDIZING BACTERIA AS VIBRIO EXTORQUENS

Stocks, Peter K. (Louisiana State University, Baton Rouge), and C. S. McCleskey. Identity of the pink-pigmented methanol-oxidizing bacteria as Vibrio extorquens. J. Bacteriol. 88:1065-1070. 1964.-Pink-pigmented bacteria isolated from enrichment cultures of methane oxidizers were found to possess similar morphological, cultural, and physiological characteristics. All the strains utilized methanol, formate, oxalate, succinate, glycerol, and benzene as sole carbon sources; methanol, formate, and glycerol afforded best growth. Most strains utilized fructose and ribose; other carbohydrates tested were not available as carbon and energy sources. There was strain variation in the use of hexane, heptane, n-propanol, n-butanol, acetate, and propionate. Methane, ethane, n-propane, and n-butane were not utilized. Our isolates, and Pseudomonas methanica of Harrington and Kallio (not the methane-dependent P. methanica of Dworkin and Foster), Pseudomonas AM1 of Peele and Quayle, Pseudomonas PRL-W4 of Kaneda and Roxburgh, and Protaminobacter ruber den Dooren de Jong are nearly identical with Vibrio extorquens (Bassalik) Bhat and Barker, and should be considered the same species.

MORPHOLOGY AND PHYSIOLOGY OF METHANOMONAS METHANOOXIDANS

Stocks, Peter K. (Louisiana State University, Baton Rouge), and C. S. McCleskey. Morphology and physiology of Methanomonas methanooxidans. J. Bacteriol. 88:1071-1077. 1964.-Pure cultures of methane-oxidizing bacteria isolated from soil, from the rumen of a fistulated cow, and from coalmine water were found to be identical in morphological, cultural, and physiological characteristics with Methanomonas methanooxidans of Brown and Strawinski. Two of the isolates were serologically related to the organism of Brown and Strawinski. All the strains required methane for good growth, but a delayed moderate growth occurred on methanol. No other substances were utilized as carbon and energy source. Nitrogen requirements were satisfied by nitrates, ammonium salts, peptone, or certain amino acids. The taxonomic position of the species is discussed.

DITERMINAL OXIDATION OF LONG-CHAIN ALKANES BY BACTERIA

Kester, A. S. (The University of Texas, Austin) and J. W. Foster. Diterminal oxidation of long-chain alkanes by bacteria. J. Bacteriol. 85:859-869. 1963.-A corynebacterial organism capable of growing in mineral salts with individual pure alkanes as carbon sources produces a series of acids from the C(10)-C(14) alkanes. They have been isolated in pure form and identified as monoic, omega-hydroxy monoic, and dioic acids containing the same number of carbon atoms as the substrate alkane. Oxidation took place at both terminal methyl groups-"diterminal oxidation." Appropriate labeling experiments indicate that omega oxidation of fatty acids occurs in this organism and that an oxygenation with O(2) occurs.

MICROBIAL GROWTH ON C1 COMPOUNDS. SYNTHESIS OF CELL CONSTITUENTS BY METHANE- AND METHANOL-GROWN PSEUDOMONAS METHANICA

1. A study has been made of the incorporation of carbon from [(14)C]methane, [(14)C]methanol and [(14)C]bicarbonate by cultures of Pseudomonas methanica growing on methane, and [(14)C]methanol by cultures of the same organism growing on methanol. 2. The distribution of radioactivity within the non-volatile constituents of the ethanol-soluble fractions of the cells, after incubation with labelled compound for periods up to 3min., has been analysed by chromatography and radioautography. 3. Over 90% of the radioactivity fixed from [(14)C]methane or [(14)C]methanol at the earliest times of sampling appeared in phosphorylated compounds. Glucose phosphate and fructose phosphate together constituted the largest part of the radioactive phosphates (70-90%); phosphoglycerate was a relatively minor component (2-17%). Other compounds becoming labelled during the incubation included glycine, serine, glutamate, aspartate, malate, citrate and alanine. 4. The first stable products of [(14)C]bicarbonate fixation were malate and aspartate (containing between them over 90% of the total radioactivity fixed at the earliest times of sampling). 5. The percentage of the total radioactivity fixed that was contained in each of the radioactive compounds has been plotted against time. The slopes of the curves obtained show that hexose phosphates are primary stable products of [(14)C]methane and [(14)C]methanol incorporation and that aspartate and malate are primary stable products of [(14)C]bicarbonate incorporation. 6. No carboxydismutase activity has been found in cell-free extracts of the organism. This fact, together with the other findings, shows that an autotrophic metabolism involving the ribulose diphosphate cycle of carbon dioxide fixation cannot be operating.

A novel porous nylon biocarrier for immobilized bacteria

A highly porous nylon biocarrier was developed to support immobilized bacteria in bioreactors used to treat liquid wastes. Porosity analyses and scanning electron microscopy showed microbial colonization of accessible pores typically in the range of 100 to 1,200 (mu)m, with some as large as 3.9 mm. A bench-scale packed-bed reactor achieved a p-nitrophenol (PNP) removal rate of 5.95 kg of PNP m(sup-3) day(sup-1) for wastes containing 1,200 mg of PNP liter(sup-1). Complete mixing of the biocarrier bed to remove excess surface biomass was routinely achieved with simple air injection. These porous polymer biocarriers are promising as microbial supports in liquid-waste treatment and bioremediation applications.

Changes in mutagenicity during crude oil degradation by fungi

Two fungal strains, Cunninghamella elegans and Penicillium zonatum, that grow with crude oil as a sole carbon source were exposed to three crude oils that exhibit a range of mutagenic activity. At regular time intervals following fungal incubation with the various crude oils, extracts were tested for the presence of mutagenic activity using the spiral Salmonella assay. When the most mutagenic of the oils, Pennsylvania crude oil, was degraded by C. elegans or by P. zonatum, its mutagenicity was significantly reduced; corresponding uninoculated (weathered) controls of Pennsylvania crude remained mutagenic. West Texas Sour crude oil, a moderately mutagenic oil, exhibited little change in mutagenicity when incubated with either C. elegans or P. zonatum. Swanson River Field crude oil from Cook Inlet, Alaska is a slightly mutagenic oil that became more mutagenic when incubated with C. elegans; weathered controls of this oil showed little change in mutagenicity. Mycelial mat weights measured during growth on crude oils increased corresponding to the biodegradation of about 25% of the crude oil.

Degradation of olestra, a non caloric fat replacer, by microorganisms isolated from activated sludge and other environments

Olestra is a non-caloric fat substitute consisting of fatty acids esterified to sucrose. Previous work has shown that olestra is not metabolized in the gut and is excreted unmodified in human feces. To better understand the fate of olestra in engineered and natural environments, aerobic bacteria and fungi that degrade olestra were enriched from sewage sludges, soils and municipal solid waste compost not previously exposed to olestra. Various mixed and pure cultures were obtained from these sources which were able to utilize olestra as a sole carbon and energy source. The fastest growing enrichment was obtained from activated sludge and later yielded an olestra-degrading pure culture of Pseudomonas aeruginosa. This mixed culture extensively degraded both 14C-fatty acid labeled olestra and 14C-sucrose labeled olestra during 8 days of incubation. Longer-term incubation with pure cultures of P.aeruginosa demonstrated that > 98% of 14C-sucrose labeled olestra and > 72% of 14C-fatty acid labeled olestra was mineralized to CO2 after 69 days. These results indicate that olestra degraders are present in environments not previously exposed to olestra and that olestra can serve as a sole carbon and energy source. Furthermore, a common bacterial species was isolated from activated sludge and shown to have the ability to degrade olestra.

Biodegradation and biotransformation of groundwater pollutant mixtures by Mycobacterium vaccae

Mycobacterium vaccae can catabolize a number of major groundwater pollutants. When added singly, acetone, cyclohexane, styrene, benzene, ethylbenzene, propylbenzene, dioxane, and 1,2-dichloroethylene can be catabolized by M. vaccae. Catabolism of a number of these chemicals was monitored by gas-chromatographic analysis. Gas-chromatographic analysis indicated that the products of benzene degradation are phenol and hydroquinone. The products of chlorobenzene and ethylbenzene degradation are 4-chlorophenol and 4-ethylphenol. The extent that some compounds were catabolized when present as mixtures was also investigated. When toluene and benzene were present concomitantly, toluene was catabolized and benzene oxidation was delayed. Although toluene promoted the degradation of styrene, a lower rate of toluene degradation occurred when styrene was present. Both 4-chlorophenol and 4-ethylphenol had an antagonistic effect on the ability of M. vaccae to degrade other aromatic compounds. Studies with [14C]benzene indicated that M. vaccae can mineralize small amounts of this compound. These results suggest that components in mixtures may have a positive or a negative effect on the rates of biodegradation of other pollutants.