Aerobic microbial degradation of glucoisosaccharinic Acid

Whole-Genome Sequence of the Anaerobic Isosaccharinic Acid Degrading Isolate, Macellibacteroides fermentans Strain HH-ZS

The ability of micro-organisms to degrade isosaccharinic acids (ISAs) while tolerating hyperalkaline conditions is pivotal to our understanding of the biogeochemistry associated within these environs, but also in scenarios pertaining to the cementitious disposal of radioactive wastes. An alkalitolerant, ISA degrading micro-organism was isolated from the hyperalkaline soils resulting from lime depositions. Here, we report the first whole-genome sequence, ISA degradation profile and carbohydrate preoteome of a Macellibacteroides fermentans strain HH-ZS, 4.08 Mb in size, coding 3,241 proteins, 64 tRNA, and 1 rRNA.

Anaerobacillus isosaccharinicus sp. nov., an alkaliphilic bacterium which degrades isosaccharinic acid

Strain NB2006^T was isolated from an isosaccharinate-degrading, nitrate-reducing enrichment culture in minimal freshwater medium at pH 10. Analysis of the 16S rRNA gene sequence indicated that this strain was most closely related to species of the newly established genus Anaerobacillus. This was supported by phenotypic and metabolic characterisation that showed that NB2006^T was rod-shaped, Gram-stain-positive, motile and formed endospores. It was an aerotolerant anaerobe and an obligate alkaliphile that grew at pH 8.5-11, could tolerate up to 6 % (w/v) NaCl, and grew at a temperature between 10 and 40 °C. In addition, it could utilise a number of organic substrates, and was able to reduce nitrate and arsenate. The predominant cellular fatty acids were C_16 : 0, C_16 : 1ω11c, anteiso-C_15 : 0, iso-C_15 : 0, C_16 : 1ω7c/iso-C_15 : 0 2-OH and C_14 : 0. The cell wall peptidoglycan contained meso-diaminopimelic acid and the DNA G+C content was 37.7 mol%. In silico DNA-DNA hybridization with the four known species of the genus Anaerobacillus showed 21.8, 21.9, 22.4, and 21.5 % relatedness to Anaerobacillusarseniciselenatis DSM 15340^T, Anaerobacilus alkalidiazotrophicus DSM 22531^T, Anaerobacillusalkalilacustris DSM 18345^T, and Anaerobacillus macyae DSM 16346^T, respectively. NB2006^T differed from strains of other species of the genus Anaerobacillus in its ability to metabolise isosaccharinate, an alkaline hydrolysis product of cellulose. On the basis of the consensus of phylogenetic and phenotypic analyses, this strain represents a novel species of the genus Anaerobacillus, for which the name Anaerobacillus isosaccharinicus sp. nov. is proposed. The type strain is NB2006^T (=DSM 100644^T=LMG 30032^T).

Ancylobacter pratisalsi sp. nov. with plant growth promotion abilities from the rhizosphere of Plantago winteri Wirtg

A Gram-negative bacterium, designated E130^T, was isolated from rhizospheric soil of Plantago winteri Wirtg. from a natural salt meadow as part of an investigation on rhizospheric bacteria from salt-resistant plant species and evaluation of their plant growth-promoting abilities. Cells were rods, non-motile, aerobic, and oxidase and catalase positive, grew in a temperature range of between 4 and 37 °C, and in the presence of 0.5-5 % NaCl (w/v). Based on 16S rRNA gene sequence analysis, strain E130^T is affiliated within the genus Ancylobacter, sharing the highest similarity with Ancylobacter rudongensis DSM 17131^T (97.6 %), Ancylobacter defluvii CCUG 63806^T (97.5 %) and Ancylobacter dichloromethanicus DSM 21507^T (97.4 %). The DNA G+C content of strain E130^T was 65.1 mol%. Its respiratory quinones were Q-9 and Q-10 and its major polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and unidentified phospholipid. Major fatty acids of the strains E130^T were C12 : 0, C16 : 0, C18 : 1ω7c and C19 : 0cycloω8c. The DNA-DNA relatedness of E130^T to A. rudongensis DSM 17131^T, A. defluvii CCUG 63806^T and A. dichloromethanicus DSM 21507^T was 29.2, 21.2 and 32.2 % respectively. On the basis of our polyphasic taxonomic study the new isolate represents a novel species, for which the name Ancylobacter pratisalsi sp. nov. is proposed. The type strain is E130^T (LMG 29367^T=DSM 102029^T).

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.0<pH>13.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

Biodegradation of the alkaline cellulose degradation products generated during radioactive waste disposal

The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and β forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and β ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7×10⁻² hr⁻¹ (SE±2.9×10⁻³). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility.

Microbial degradation of isosaccharinic acid at high pH

Intermediate-level radioactive waste (ILW), which dominates the radioactive waste inventory in the United Kingdom on a volumetric basis, is proposed to be disposed of via a multibarrier deep geological disposal facility (GDF). ILW is a heterogeneous wasteform that contains substantial amounts of cellulosic material encased in concrete. Upon resaturation of the facility with groundwater, alkali conditions will dominate and will lead to the chemical degradation of cellulose, producing a substantial amount of organic co-contaminants, particularly isosaccharinic acid (ISA). ISA can form soluble complexes with radionuclides, thereby mobilising them and posing a potential threat to the surrounding environment or ‘far field'. Alkaliphilic microorganisms sampled from a legacy lime working site, which is an analogue for an ILW-GDF, were able to degrade ISA and couple this degradation to the reduction of electron acceptors that will dominate as the GDF progresses from an aerobic ‘open phase' through nitrate- and Fe(III)-reducing conditions post closure. Furthermore, pyrosequencing analyses showed that bacterial diversity declined as the reduction potential of the electron acceptor decreased and that more specialised organisms dominated under anaerobic conditions. These results imply that the microbial attenuation of ISA and comparable organic complexants, initially present or formed in situ, may play a role in reducing the mobility of radionuclides from an ILW-GDF, facilitating the reduction of undue pessimism in the long-term performance assessment of such facilities.

The Identification and Degradation of Isosaccharinic Acid, a Cellulose Degradation Product

Nirex is seeking to develop a deep underground repository for the disposal of solid intermediate-level and low-level radioactive wastes (ILW and LLW) in the UK. One possible influence on the behaviour of radionuclides is the formation of water-soluble complexants by the degradation of the solid organic polymers that will be present in the wastes. The degradation products of cellulose have been shown to increase the solubility of plutonium and other radionuclides and to reduce sorption onto near-field and far-field materials. Degradation of cellulose under anaerobic alkaline conditions produces a range of organic acids. In this paper 2-C-(hydroxymethyl)-3-deoxy-D-pentonic acid (isosaccharinic acid, ISA) is identified by High Performance Liquid Chromatography as a significant component of cellulose leachates. A combination of fractionation of cellulose leachates and plutonium solubility determinations shows that ISA is responsible for the majority of the enhancement of plutonium solubility observed in such leachates. Further degradation of ISA by chemical or microbial action may lessen the effect of degraded cellulose leachates. Experimental studies on the chemical degradation of this compound under alkaline conditions suggest that the presence of oxygen is required. Microbial degradation studies show that the plutonium solubility in solutions of ISA is reduced by their exposure to microbial action.

Molecular analysis of bacterial isolates and total community DNA from kraft pulp mill effluent treatment systems

Chloroaliphatics are major components of bleached kraft mill effluents. Gene probes and oligonucleotide primers were developed to monitor kraft pulp mill effluent treatment systems for the presence of key genes (dehalogenases) responsible for the dehalogenation of chloroaliphatic organics. The primers were used for polymerase chain reaction (PCR) analysis of genomic DNA extracted from dehalogenating bacterial isolates and from total community DNA extracted from water and sediments of mill effluent treatment systems. PCR amplification with oligonucleotide primers designed from dhlB, encoding the haloacid dehalogenase from Xanthobacter autotrophicus, revealed the presence of dehalogenase genes in both aerated lagoons and stabilization basins. Similarly, positive results were obtained with mmoX primers designed from the soluble methane monooxygenase gene of Methylococcus capsulatus Bath. The haloacetate dehalogenase encoding gene (dehH2) from Moraxella sp. was typically not detected in mill effluent treatment systems unless the biomass was selectively enriched. DNA sequence analysis of several PCR fragments revealed significant similarity to known dehalogenase and methane monooxygenase genes. The results indicated a broad distribution of known dehalogenation genes and bacteria with chloroorganic-degrading potential in the mill effluent treatment systems.Key words: dehalogenase, gene probes, chloroorganics, PCR, mill effluents.