Electrochemical checking of aerobic isolates from electrochemically active biofilms formed in compost

AIMS

To design a cyclic voltammetry (CV) procedure to check the electrochemical activity of bacterial isolates that may explain the electrochemical properties of biofilms formed in compost.

METHODS AND RESULTS

Bacteria catalysing acetate oxidation in garden compost were able to form electrochemically active biofilms by transferring electrons to an electrode under chronoamperometry. They were recovered from the electrode surface and identification of the isolates using 16S rRNA sequencing showed that most of them were Gammaproteobacteria, mainly related to Enterobacter and Pseudomonas spp. A CV procedure was designed to check the electrochemical activity of both groups of isolates. Preliminary CVs suggested that the bacteria were not responsible for the catalysis of acetate oxidation. In contrast, both groups of isolates were found to catalyse the electrochemical reduction of oxygen under experimental conditions that favoured adsorption of the microbial cells on the electrode surface.

CONCLUSIONS

Members of the genera Enterobacter and Pseudomonas were found to be able to catalyse the electrochemical reduction of oxygen.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has shown the unexpected efficiency of Enterobacter and Pseudomonas spp. in catalysing the reduction of oxygen, suggesting a possible involvement of these species in biocorrosion, or possible application of these strains in designing bio-cathode for microbial fuel cells.

Deferribacter abyssi sp. nov., an anaerobic thermophile from deep-sea hydrothermal vents of the Mid-Atlantic Ridge

Two strains of thermophilic, anaerobic, chemolithoautotrophic bacteria, designated JR(T) and DR, were isolated from hydrothermal samples collected on the Mid-Atlantic Ridge from the Rainbow (36 degrees 16' N, 33 degrees 54' W) and Menez Gwen (37 degrees 50' N, 31 degrees 50' W) vent fields, respectively. Cells of both isolates were short, straight- to vibrio-shaped, motile rods with one polar flagellum, and were Gram-negative and non-sporulating. Strain JR(T) was characterized in detail. It was found to grow optimally at pH 6.5-6.7, at 60 degrees C and in the presence of 30 g NaCl l(-1). Strain JR(T) could use molecular hydrogen, acetate, succinate, pyruvate and proteinaceous compounds as electron donors, and elemental sulfur, nitrate or Fe(III) as electron acceptors. No fermentation of organic substrates occurred. The G+C content of the DNA of strain JR(T) was 30.8 mol%. Strain DR (=DSM 14927) possessed the same morphology and pH, temperature and salinity optima and ranges, and used the same electron acceptors as strain JR(T). On the basis of their 16S rDNA sequences (1517 nucleotides), strains JR(T) and DR were identical and distantly related to Deferribacter thermophilus and Deferribacter desulfuricans (95.3 and 95.2 % sequence similarity, respectively). Based on their phenotypic and phylogenetic characteristics, it is proposed that both strains are members of a new species of the genus Deferribacter, for which the name Deferribacter abyssi (type strain JR(T)=DSM 14873(T)=JCM 11955(T)) is proposed.

Vulcanithermus mediatlanticus gen. nov., sp. nov., a novel member of the family Thermaceae from a deep-sea hot vent

A novel thermophilic, microaerophilic, facultatively chemolithoheterotrophic bacterium designated strain TR(T) was isolated from a sample of a deep-sea hydrothermal chimney collected at the Rainbow vent field on the Mid-Atlantic Ridge (36 degrees 14'N). Gram-negative, non-spore-forming, non-motile rods occurred singly or in pairs. The organism grew in the temperature range 37-80 degrees C with an optimum at 70 degrees C and at pH 5.5-8.4 with an optimum around 6.7. The NaCl range for growth was 10-50 g l(-1) with an optimum of 30 g l(-1). Strain TR(T) grew chemoorganoheterotrophically with carbohydrates, proteinaceous substrates, organic acids and alcohols using oxygen or nitrate as electron acceptors. The isolate was able to grow at oxygen concentrations from 0.5 to 21%. Oxygen concentrations that promoted fastest growth ranged from 4 to 8% under agitation. The novel isolate was able to grow lithoheterotrophically with molecular hydrogen as the energy source. The G + C content of the genomic DNA was 68.4 mol%. Phylogenetic analysis of the 16S rDNA sequence placed strain TR(T) within the phylum Deinococcus-Thermus of the Bacteria. On the basis of phenotypic and phylogenetic data, it is proposed that this isolate should be described as a member of a novel species of a new genus as Vulcanithermus mediatlanticus gen. nov., sp. nov. The type strain is TR(T) (= DSM 14978T = VKM B-2292T = JCM 11956T).

Intrapelvic migration of total hip prostheses. Operative treatment

We describe a safe operative approach for removal of a prosthesis that has migrated into the pelvis, and we recommend that a two-stage reconstruction be done when revising the total hip-replacement arthroplasty. The first stage consists of the removal of the femoral component and cement through a lateral transtrochanteric approach, followed by removal of the acetabular component through an abdominal-retroperitoneal approach to permit exposure of the major intrapelvic structures and to ascertain their relationship to the acetabular component and cement. After the acetabular component has been removed, bone grafts are applied to the pelvis. Postoperatively, the patient is placed in traction for a time and then is allowed to walk with non-weight-bearing. The second stage of reconstruction, consisting of hip replacement, is performed nine to twelve months after the first stage. A satisfactory result was obtained in the four patients for whom we followed this operative regimen. In one patient, the first-stage procedure yielded a satisfactory result and the second stage was not done.

Cartilaginous exostosis arising from the ventral surface of the scapula. A case report

Osteochondromas of the scapula are not rare in occurrence, especially in multiple hereditary exostosis. A scapular exostosis, excised from the ventral surface of the scapula in a 13-year-old girl, produced symptoms of shoulder pain.

Incidence and mechanism of failure of cemented acetabular component in total hip arthroplasty

Clinical results today seem to suggest that acrylic cement is crucial in producing immediate and reproducible results of pain-free joints following total hip replacement. Proper application by the use of contemporary techniques may be suitable in most conditions requiring hip replacement. The incidence of acetabular failure in a specific group of patients at risk may warrant experimentation by the use of a noncemented system. The mechanism of failure of low-friction arthroplasty may be multifaceted, but our experience indicates that the mechanisms of failure of the acetabulum have been due to excessive deepening and expansion of the acetabulum, once thought to be fundamental to the procedure. A rudimentary technique of cement pressurization, both in the femur and in the acetabulum, also may have played a part in late failures of this procedure. Early demarcation at the cement-bone interface was prevalent in young and active or heavy individuals. Demarcation and loosening were time-dependent phenomena. Demarcation and loosening also appeared with the aging process and increased osteopenia. A higher incidence of loosening also was observed in young and light-weight individuals, with presumably increased elasticity of the pelvic bone.