Single Microorganism Research Articles

Ultrastructural detection of an unusual intranuclear bacterium in Pentastiridius leporinus (Hemiptera: Cixiidae)

Pentastiridius leporinus is an important vector of sugar beet pathogens in eastern France. An electron microscope survey on the insect-associated microflora revealed the occurrence of intranuclear prokaryotic cells in every internal organ analysed. These bacteria, which could also be found in the cytoplasm surrounding the nucleus, had a homogeneous coccoid (ca. 0.45 μm) or rod (0.45–1 μm) shape. The presence of three membrane layers was observed, the outermost forming a kind of vacuole containing generally a single microorganism. No cytopathological abnormalities were detected in the infected cells. To our knowledge, this is the first report of a hemipteran species infected by intranuclear bacteria. The possible identity of this microorganism is discussed.

Study on the increase mechanism of the caffeine content during the fermentation of tea with microorganisms

The tea caffeine content had previously been shown to increase reasonably after being treated with mixed microorganisms for a period of time. In this study, single microorganisms were used in the fermentation of black and green teas in order to find which microorganism has the best effect on increasing the caffeine content. The results demonstrated that molds fermentation increased the caffeine content, but yeasts fermentation decreased the caffeine content. Among the three molds in this study, Aspergillus niger van Tieghem has the most remarkable effect, and the caffeine content in dry green tea increased from an initial 3.47% to 9.63%. The increase rate was 177.5% on the 16th day. Furthermore, the changes of caffeine and theophylline were of a similar trend. Possibly theophylline instead of theobromine is the precursor of caffeine in the living microorganisms. The new biosynthetic route is different from that in tea plants.

Toxic action and antibiotic in the chemostat: permanence and extinction of a model with functional response

A system of periodic coefficients functional differential equations is used to model the single microorganism in the chemostat environment with a periodic nutrient and antibiotic input. Furthermore, the total toxic action on the microorganism expressed by an integral term is considered in our system. Based on the technique of analysis, we obtain sufficient conditions which guarantee the permanence of the system and extinction of the microorganism.

Replacement of fish oil with thraustochytrid Schizochytrium sp. L oil in Atlantic salmon parr ( Salmo salar L) diets

Replacing fish oil with that from a docosahexaenoic acid (22:6ω3, DHA) rich single cell micro-organism, thraustochytrid Schizochytrium sp. L, in diets for Atlantic salmon ( Salmo salar) was investigated. Four experimental diets containing 100% thraustochytrid oil (TO), 100% palm oil (PO) and a 4:1 palm and thraustochytrid oil mixture (MX) were compared to a fish oil (FO) diet over 9 weeks. A saltwater transfer challenge occurred at the end of the trial for 14 days to test the diet treatments on the ability of salmon to smolt. There were no significant differences in the feed consumption of the diets or the digestibility of the ω3 or ω6 PUFA, indicating no differences in the digestibility of fatty acids between diets. No significant differences were noted between the growth of fish on the four diet treatments. Significant differences were noted in the fatty acid profiles of the fish muscle tissues between all diets. Fish on the TO diet had a significantly greater percentage of DHA in muscle tissue compared with fish on all other diets. Blood osmolarity, which is inversely related to the ability of salmon to smolt, from the TO and FO fed fish was significantly lower than that of fish on the PO diet. This study showed that thraustochytrid oil can be used to replace fish oil in Atlantic salmon diets without detriment to the growth of parr. Including thraustochytrid oil in fish diets significantly increases the amount of DHA in Atlantic salmon muscle and therefore is a candidate for use in oil blends for salmon diets. Thraustochytrid oil provides a renewable source of essential fatty acids, in particular DHA, for aquafeeds.

Epstein-Barr Virus: Environmental Trigger of Multiple Sclerosis?

Autoimmune diseases affect approximately 5% of the population in the United States and are the third most common disease category after cancer and heart disease. At least 15 diseases are known to be the direct result of an autoimmune response, while circumstantial evidence implicates autoimmunity in more than 80 conditions. Multiple sclerosis (MS), autoimmune skin and thyroid diseases, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA) are among the most prevalent disorders in this category. Diseases of autoimmune origin are generally believed to arise from unfortunate combinations of genetic susceptibility and environmental insults. HLA-DR and -DQ alleles within the HLA class II region on chromosome 6 are by far the strongest risk-conferring genes for most of the aforementioned entities. Viral and bacterial infections are logical candidates as environmental triggers. However, for the numerous agents that have been linked with specific autoimmune diseases based on serology, pathology, or virus isolation, none of the postulated associations has been conclusive. The difficulty in identifying a causative single microorganism might indicate that Koch's paradigm, “one organism, one disease,” does not apply to such complex diseases and suggests that several different agents can induce or exacerbate autoimmune diseases and that these are most likely ubiquitous pathogens of a high prevalence in the population (37, 69). Epstein-Barr virus (EBV) has been a leading candidate trigger for several autoimmune diseases since the initial description of raised EBV-specific antibody titers in patients with SLE in 1971 (23). EBV is a biologically plausible candidate since it is ubiquitous in nature, establishes a lifelong dormant infection with continuous virus production due to reactivation, and modulates the human immune system. In its immune-modifying function, EBV rescues infected B cells via latent antigen expression and assists their differentiation into memory B cells, in which it persists. In addition, the virus continuously stimulates strong T-cell responses via chronic antigen presence, and this immune control is crucial to prevent EBV-associated malignancies. Recent studies indicate that EBV-specific cellular and humoral immune responses and the regulation of viral persistence in EBV-infected memory B cells are altered in patients with autoimmune diseases (3, 29, 38, 52, 54, 79, 80). In MS patients, longitudinal analyses of serum samples collected more than 10 years before the onset of clinical symptoms consistently showed that the risk of developing the disease increased significantly with the level of EBV antibody titers, and the strongest association was found for immunoglobulin G (IgG) antibodies binding to a EBV latent antigen, nuclear antigen 1 (EBNA1) (3, 21, 46). The mechanisms responsible for the association of EBV infection and the evolution of MS have so far not been clarified. In this review, we will discuss new evidence and hypotheses for a potential linkage between host-EBV interactions and the initiation as well as maintenance of autoimmune diseases. Since the existing literature suggests that different mechanisms lead to EBV association with the various autoimmune diseases, we will focus our discussion primarily on MS and refer to SLE and RA only when similarities or differences between these diseases and MS have been clearly defined.

Dialkylphosphonodibromo-acetates and -acetonitriles as potential new biocides

The preparation of several alkyl dialkylphosphonodibromoacetates and dialkylphosphonodibromoacetonitriles is described. Some of these materials were shown to possess interesting biocidal characteristics both against single micro-organisms and against wild type mixed micro-organisms present in cooling water from a fertiliser plant.

O-CAS, a fast and universal method for siderophore detection

In this work, the popular CAS assay for siderophore detection, based on the utilization of chrome azurol S, was redesigned and optimized to produce a new, fast, non-toxic, and easy method to determine a wide variety of microorganisms capable of siderophore production on a solid medium. Furthermore, this specific bioassay allows for the identification of more than one single siderophore-producing microorganism at the same time, using an overlay technique in which a modified CAS medium is cast upon culture agar plates (thus its name “O-CAS”, for overlaid CAS). Detection was optimized through adjustments to the medium's composition and a quantifying strategy. Specificity of the bioassay was tested on microorganisms known for siderophore production. As a result, a total of 48 microorganisms were isolated from three different types of samples (fresh water, salt water, and alkaline soil), of which 36 were determined as siderophore producers. The compounds identified through this method belonged to both hydroxamate and catechol-types, previously reported to cause color change of the CAS medium from blue to orange and purple, respectively. Some isolated microorganisms, however, caused a color change that differed from previous descriptions.

Single-Cell Detection: Test of Microbial Contamination Using Capillary Electrophoresis

Single cells of bacteria and fungi were detected using a capillary electrophoresis-based test for microbial contamination in laboratory samples. This technique utilizes a dilute cationic surfactant buffer to sweep microorganisms out of the sample zone and a small plug of "blocking agent" to negate the cells' mobility and induce aggregation. Analysis times are generally under 10 min. Previously, a nutrient broth media was reported as an effective blocking agent; however, the natural background fluorescence from the nutrient broth limited the detection sensitivity to approximately 50 cells. In order to enhance the sensitivity of the technique down to a single cell, an alternative synthetic blocking agent was sought. Various potential blocking agents were screened including salts, polypeptides, small organic zwitterions, and surfactants. Zwitterionic surfactants are shown to be attractive alternatives to a nutrient broth blocker and mimic the nutrient broth's effects on cellular aggregation and mobility. Specifically, caprylyl sulfobetaine provided the sharpest cell peaks. By substituting caprylyl sulfobetaine in place of the nutrient broth, the fluorescence of the blocker plug was reduced by as much as 40 x. This reduction in background noise enables detection of a single microorganism in a sample and allows this technique to be potentially used as a rapid sterility test. All single cells analyzed using this technique displayed signal-to-noise ratios between 5 and 9.

Data storm

Data storm

Coexpression of two detoxifying pesticide-degrading enzymes in a genetically engineered bacterium

Abstract Degradation of pesticides is usually beneficial, since the reactions that destroy pesticides convert most pesticide residues in the environment to inactive, less toxic, harmless compounds. This paper describes a novel strategy using a coexpression vector for the purpose of developing bacteria that can detoxify different pesticides. The vector pETDuet was designed for coexpression of two target genes simultaneously. The organophosphate hydrolase gene (opd) from Flavobacterium sp. and carboxylesterase B1 gene (b1) from Culex pipiens were cloned in the coexpression vector. The expressed enzymes of OPH and B1 had a molecular mass of approximately 35 and 65 kDa, respectively. A single microorganism was capable of producing both enzymes for degradation of organophosphorus, carbamate and pyrethroid pesticides. The technical capability of genetically engineering bacteria with more enzymes should open up new opportunities for extending the wide range of pesticides that can be biodegraded in the future.

Decolourization of a textile-reactive dye with Phanerochaete chrysosporium incubated in different ways under non-sterile conditions

Most studies on decolourization of reactive dye with Phanerochaete chrysosporium have been performed under sterile conditions. In this paper, Phanerochaete chrysosporium, suspended in liquid medium, immobilized on nylon nets, and immobilized on polyurethane foams were studied to decolorize a textile-reactive dye in agitated liquid incubation under non-sterile conditions. The results showed that the decolourization against reactive brilliant red K-2BP by mycelia pellets in suspended cultures, the fungi immobilized on nylon nets and immobilized on polyurethane foams were 0%, 52% and 95%, respectively. The suspended incubation system and the system with nylon nets were contaminated with yeasts, which deteriorated the decolourization effects. The three-dimensional reticular structure of polyurethane foam was benefit to Phanerochaete chrysosporium growth in spreading mycelia taking nutrients and oxygen effectively. The foam could quickly absorb liquid medium into its holes, leaving much less nutrients to support the growth of single cell micro-organisms such as yeast in liquid. The micro-environment existed in polyurethane foam was close to the wild growth conditions of white rot fungus in nature. In conclusion, immobilized culture with polyurethane foam carriers is advantaged to reduce the colonization of other micro-organisms, and makes Phanerochaete chrysosporium possess higher decolorizing ability under non-sterile conditions.

Immunohistochemical evidence of Clostridium sp, Staphylococcus aureus, and group A Streptococcus in severe soft tissue infections related to injection drug use

Severe soft tissue infections are caused by either single or multiple microorganisms. We performed a retrospective immunohistochemical (IHC) study on formalin-fixed, paraffin-embedded soft tissue samples from 20 injection drug users who were part of a cluster of severe illness and death after skin and soft tissue infections in Scotland and Ireland in 2000. The IHC assays used antibodies against Clostridium sp, Staphylococcus aureus, group A streptococci, and Bacillus anthracis. Intact bacilli and granular Clostridium antigen staining in areas with necrosis, edema, and inflammation were observed in skin, fascia, or muscle samples of 12 (60%) patients. A variety of clostridia were isolated from affected soft tissues in 10 IHC-positive cases. Staphylococcus aureus antigens were observed in 3 cases including 1 where S aureus was isolated, 1 with negative cultures, and 1 where mixed cultures were obtained. Group A streptococcal antigens were observed in 1 case in which Streptococcus pyogenes and S aureus were isolated. By using IHC, we detected different bacteria in archival soft tissue samples from patients with severe skin and soft tissue infections. Immunohistochemical assays can be of great diagnostic value, particularly for bacteria such as Clostridium sp, which are difficult to isolate because of their anaerobic fastidious growth requirements.

Beyond Our Pages

Beyond Our Pages

Efficient NADPH Recycling in Enantioselective Bioreduction of a Ketone with Permeabilized Cells of a Microorganism Containing a Ketoreductase and a Glucose 6‐Phosphate Dehydrogenase

AbstractWe have demonstrated, for the first time, the efficient recycling of NADPH in a bioreduction with permeabilized cells of a single microorganism. Permeabilized cells of Bacillus pumilus Phe‐C3 containing an NADPH‐dependent ketoreductase and a glucose 6‐phosphate dehydrogenase (G‐6‐PDH) were successfully used for the reduction of ethyl 3‐oxo‐4,4,4‐trifluorobutanoate (1) to give (R)‐ethyl 3‐hydroxy‐4,4,4‐trifluorobutanoate (2) in 95% ee with the recycling of NADPH for 4220 times from the externally added NADP+. The permeabilized cells were shown to be stable and active for a long period, allowing for high product concentration with high cofactor TTN by continuing the bioreduction with renewed addition of NADP+. This provides with not only a practical synthesis of (R)‐2 but also a useful method applicable to many microbial oxidoreductions, since G‐6‐PDH is a very common enzyme existing in many microorganisms.

Modeling product formation in anaerobic mixed culture fermentations

The anaerobic conversion of organic matter to fermentation products is an important biotechnological process. The prediction of the fermentation products is until now a complicated issue for mixed cultures. A modeling approach is presented here as an effort to develop a methodology for modeling fermentative mixed culture systems. To illustrate this methodology, a steady-state metabolic model was developed for prediction of product formation in mixed culture fermentations as a function of the environmental conditions. The model predicts product formation from glucose as a function of the hydrogen partial pressure (P(H2)), reactor pH, and substrate concentration. The model treats the mixed culture as a single virtual microorganism catalyzing the most common fermentative pathways, producing ethanol, acetate, propionate, butyrate, lactate, hydrogen, carbon dioxide, and biomass. The product spectrum is obtained by maximizing the biomass growth yield which is limited by catabolic energy production. The optimization is constrained by mass balances and thermodynamics of the bioreactions involved. Energetic implications of concentration gradients across the cytoplasmic membrane are considered and transport processes are associated with metabolic energy exchange to model the pH effect. Preliminary results confirmed qualitatively the anticipated behavior of the system at variable pH and P(H2) values. A shift from acetate to butyrate as main product when either P(H2) increases and/or pH decreases is predicted as well as ethanol formation at lower pH values. Future work aims at extension of the model and structural validation with experimental data.

The role of selective decontamination of the digestive tract in acute stroke

following a stroke, morbidity and mortality is high, with aspiration pneumonia being a common complication. to determine the levels of colonisation by and isolation of aerobic Gram-negative bacteria (AGNB) in acute stroke patients and determine the effect of selective decontamination of the digestive tract (SDD) on oral flora and whether it reduces both morbidity and mortality after an acute stroke. a prospective, randomised, placebo-controlled double blind trial. acute stroke assessment units of three hospitals in the northwest of England. 203 patients admitted to hospital following a first acute stroke. participants were randomised to SDD oral gel or placebo. Swallow was assessed on admission to hospital, and oral swabs were obtained thrice weekly. Demographic and clinical data were recorded. 203 patients (106 males and 97 females) participated, of whom 20 died during their hospitalisation, 19 withdrew and full follow-up was obtained for the remaining 164. A total of 122 AGNB were isolated in 105 samples from 48 patients. Abnormal swallow on admission was found in 58 patients (29%). A total of 34 patients carried a single gram-negative micro-organism that was present on one or more occasions. More than one AGNB was carried in 14 patients, and organisms were significantly more likely to be isolated from the placebo group than the active group during weeks 2 and 3 of treatment (P = 0.034, chi-squared). Seven patients in the placebo group and one in the treatment group developed pneumonia (P = 0.029, Fisher's exact test). high carriage of and colonisation by AGNB was found within this study, which was reduced by the addition of SDD. Although SDD reduced the presence of both organisms and documented episodes of pneumonia, mortality remained unchanged.

Endoscopically Guided Aerobic Cultures in Postsurgical Patients with Chronic Rhinosinusitis

There is considerable amount of debate in the literature regarding the microbial flora of normal, acutely infected, and chronically infected paranasal sinuses. Few studies have specifically looked at the microbial flora of healthy and infected sinus cavities after functional endoscopic sinus surgery. One hundred thirty-four cultures were studied. All cultures were obtained using a standard technique. The nasal cavities were decongested and anesthetized, and nasal endoscopy was performed. When purulent secretions were identified, specimens of purulent secretions were obtained for incubation. Sensitivities were tested according to microorganisms identified. Empiric therapy generally consisted of afluoroquinolone, amoxicillin/clavulanate, or a later-generation cephalosporin, and adjustment in individual instances when appropriate. Twelve cultures showed no growth, 86 grew a single microorganism, and 35 grew two or more microorganisms for a total of 151 microorganisms identified. The most common microorganisms were Staphylococcus aureus, coagulase-negative staphylococci, and Pseudomonas aeruginosa. Other organisms that were cultured <5% of the time included Streptococcus pneumoniae, Haemophilus influenza, Moraxella catarrhalis, Serratia liquefaciens, Stenotrophomonas (Xanthomonas) maltophilia, alcaligenes, Fusobacterium, Escherichia coli, diphtheroids, Acinetobacter species, Klebsiella species, skin flora, and mixed Gram-negative and Gram-positives. Endoscopically guided aerobic cultures in postsurgical patients with acute exacerbations of chronic rhinosinusitis most commonly grew S. aureus, coagulase-negative staphylococci, and pseudomonal species. These cultures altered antibiotic treatment management decisions in a significant number of cases regardless of patients' clinical characteristics or history of previous culture.

K Codell Carter, The rise of causal concepts of disease: case histories, The History of Medicine in Context, Aldershot, Ashgate, 2003, pp. ix, 237, £55.00 (hardback 0-7546-0678-3).

K Codell Carter, The rise of causal concepts of disease: case histories, The History of Medicine in Context, Aldershot, Ashgate, 2003, pp. ix, 237, £55.00 (hardback 0-7546-0678-3).

Bacteriology of Chronic Dacryocystitis in a Tertiary Eye Care Center

To determine the current bacteriology of adult chronic dacryocystitis in a tertiary eye care center and compare it with previously reported studies. Clinical and microbiological records of patients with diagnosis of chronic dacryocystitis between January 1999 and March 2002 were reviewed for age, sex, lacrimal sac side involved, and culture results. Patients younger than 16 years of age and patients who were receiving any systemic or topical antibiotics were excluded from the study. One hundred eighty-eight adult patients with an average age of 50.5 years (range, 16 to 91 years), who had a diagnosis of chronic dacryocystitis, were identified. The study was predominated by female subjects (65.4%). Of the cultures from the nasolacrimal sac, 183 (97.3%) were positive for bacteria, with an average of 2.3 (1 to 6) microorganisms. More than 2 microorganisms were present in 66.1% of the cultures, whereas a single microorganism was recovered from 33.9% of the cultures. The majority of microorganisms in our study were Gram-positive bacteria, representing 53.7% of the overall microorganisms cultured with a predominance of Staphylococcus species. Gram-negative bacteria were recovered from 26.0% of the specimens with predominance of Haemophilus influenzae. Anaerobic microorganisms were present in 19.1% of the samples. The most frequently isolated anaerobic microorganisms were Propionibacterium acne and Peptostreptococcus species. Several bacterial species may be involved in the pathogenesis of chronic dacryocystitis in adults, and the majority of patients harbor multiple microorganisms in their nasolacrimal sacs. The high rate of microorganism-positive lacrimal sac cultures suggests that adult patients should be treated for their infection before any intraocular surgery because of the potential risk of infection.

TEM study of a silicate-carbonate-microbe interface prepared by focused ion beam milling

The biogeochemical alteration of an Mg-Fe orthopyroxene, reacted for 70 yr under arid conditions in a desert environment, was studied by transmission electron microscopy. For this purpose, an electron transparent cross-section of the interface between a single microorganism, an orthopyroxene and nanometer-sized calcite crystals, was prepared with a focused ion beam system. X-ray energy dispersive spectrometry and electron energy loss spectroscopy allowed one to clearly distinguish the microorganism en route to fossilization from the nanometer-sized calcite crystals, showing the usefulness of such a protocol for identifying unambiguously traces of life in rocks. A 100-nm-deep depression was observed in the orthopyroxene close to the microorganism, suggesting an enhanced dissolution mediated by the microbe. However, an Al- and Si-rich amorphous altered layer restricted to the area just below the microorganism could be associated with decreased silicate dissolution rates at this location, suggesting complex effects of the microorganism on the silicate dissolution process. The close association observed between silicate dissolution and carbonate formation at the micrometer scale suggests that Urey-type CO 2 sequestration reactions could be mediated by microorganisms under arid conditions.