Methanogenic partner influences cell aggregation and signalling of Syntrophobacterium fumaroxidans

For several decades, the formation of microbial self-aggregates, known as granules, has been extensively documented in the context of anaerobic digestion. However, current understanding of the underlying microbial-associated mechanisms responsible for this phenomenon remains limited. This study examined morphological and biochemical changes associated with cell aggregation in model co-cultures of the syntrophic propionate oxidizing bacterium Syntrophobacterium fumaroxidans and hydrogenotrophic methanogens, Methanospirillum hungatei or Methanobacterium formicicum. Formerly, we observed that when syntrophs grow for long periods with methanogens, cultures tend to form aggregates visible to the eye. In this study, we maintained syntrophic co-cultures of S. fumaroxidans with either M. hungatei or M. formicicum for a year in a fed-batch growth mode to stimulate aggregation. Millimeter-scale aggregates were observed in both co-cultures within the first 5 months of cultivation. In addition, we detected quorum sensing molecules, specifically N-acyl homoserine lactones, in co-culture supernatants preceding the formation of macro-aggregates (with diameter of more than 20 μm). Comparative transcriptomics revealed higher expression of genes related to signal transduction, polysaccharide secretion and metal transporters in the late-aggregation state co-cultures, compared to the initial ones. This is the first study to report in detail both biochemical and physiological changes associated with the aggregate formation in syntrophic methanogenic co-cultures. KEYPOINTS: • Syntrophic co-cultures formed mm-scale aggregates within 5 months of fed-batch cultivation. • N-acyl homoserine lactones were detected during the formation of aggregates. • Aggregated co-cultures exhibited upregulated expression of adhesins- and polysaccharide-associated genes.

Characterization of Amycolatopsis 75iv2 dye-decolorizing peroxidase on O-glycosides

Dye-decolorizing peroxidases are heme peroxidases with a broad range of substrate specificity. Their physiological function is still largely unknown, but a role in the depolymerization of plant cell wall polymers has been widely proposed. Here, a new expression system for bacterial dye-decolorizing peroxidases as well as the activity with previously unexplored plant molecules are reported. The dye-decolorizing peroxidase from Amycolatopsis 75iv2 (DyP2) was heterologously produced in the Gram-positive bacterium Streptomyces lividans TK24 in both intracellular and extracellular forms without external heme supplementation. The enzyme was tested on a series of O-glycosides, which are plant secondary metabolites with a phenyl glycosidic linkage. O-glycosides are of great interest, both for studying the compounds themselves and as potential models for studying specific lignin-carbohydrate complexes. The primary DyP reaction products of salicin, arbutin, fraxin, naringin, rutin, and gossypin were oxidatively coupled oligomers. A cleavage of the glycone moiety upon radical polymerization was observed when using arbutin, fraxin, rutin, and gossypin as substrates. The amount of released glucose from arbutin and fraxin reached 23% and 3% of the total substrate, respectively. The proposed mechanism suggests a destabilization of the ether linkage due to the localization of the radical in the para position. In addition, DyP2 was tested on complex lignocellulosic materials such as wheat straw, spruce, willow, and purified water-soluble lignin fractions, but no remarkable changes in the carbohydrate profile were observed, despite obvious oxidative activity. The exact action of DyP2 on such lignin-carbohydrate complexes therefore remains elusive.

IMPORTANCE

Peroxidases require correct incorporation of the heme cofactor for activity. Heterologous overproduction of peroxidases often results in an inactive enzyme due to insufficient heme synthesis by the host organism. Therefore, peroxidases are incubated with excess heme during or after purification to reconstitute activity. S. lividans as a production host can produce fully active peroxidases both intracellularly and extracellularly without the need for heme supplementation. This reduces the number of downstream processing steps and is beneficial for more sustainable production of industrially relevant enzymes. Moreover, this research has extended the scope of dye-decolorizing peroxidase applications by studying naturally relevant plant secondary metabolites and analyzing the formed products. A previously overlooked artifact of radical polymerization leading to the release of the glycosyl moiety was revealed, shedding light on the mechanism of DyP peroxidases. The key aspect is the continuous addition, rather than the more common approach of a single addition, of the cosubstrate, hydrogen peroxide. This continuous addition allows the peroxidase to complete a high number of turnovers without self-oxidation.

Interactions of Natural Flavones with Iron Are Affected by 7-O-Glycosylation, but Not by Additional 6″-O-Acylation

In iron-fortified bouillon, reactivity of the iron ion with (acylated) flavone glycosides from herbs can affect product color and bioavailability of iron. This study investigates the influence of 7-O-glycosylation and additional 6″-O-acetylation or 6″-O-malonylation of flavones on their interaction with iron. Nine (6″-O-acylated) flavone 7-O-apiosylglucosides were purified from celery (Apium graveolens), and their structures were elucidated by mass spectrometry (MS) and nuclear magnetic resonance (NMR). In the presence of iron, a bathochromic shift and darker color were observed for the 7-O-apiosylglucosides compared to the aglycon of flavones that only possess the 4-5 site. Thus, the ability of iron to coordinate to the flavone 4-5 site is increased by 7-O-glycosylation. For flavones with an additional 3'-4' site, less discoloration was observed for the 7-O-apiosylglucoside compared to the aglycon. Additional 6″-O-acylation did not affect the color. These findings indicate that model systems used to study discoloration in iron-fortified foods should also comprise (acylated) glycosides of flavonoids.

Insights in the Recalcitrance of Theasinensin A to Human Gut Microbial Degradation

Due to low bioavailability of dietary phenolic compounds in small intestine, their metabolism by gut microbiota is gaining increasing attention. The microbial metabolism of theasinensin A (TSA), a bioactive catechin dimer found in black tea, has not been studied yet. Here, TSA was extracted and purified for in vitro fermentation by human fecal microbiota, and epigallocatechin gallate (EGCG) and procyanidin B2 (PCB2) were used for comparison. Despite the similarity in their flavan-3-ol skeletons, metabolic fate of TSA was distinctively different. After degalloylation, its core biphenyl-2,2',3,3',4,4'-hexaol structure remained intact during fermentation. Conversely, EGCG and PCB2 were promptly degraded into a series of hydroxylated phenylcarboxylic acids. Computational analyses comparing TSA and PCB2 revealed that TSA's stronger interflavanic bond and more compact stereo-configuration might underlie its lower fermentability. These insights in the recalcitrance of theasinensins to degradation by human gut microbiota are of key importance for a comprehensive understanding of its health benefits.

Configuration of active site segments in lytic polysaccharide monooxygenases steers oxidative xyloglucan degradation

BACKGROUND

Lytic polysaccharide monooxygenases (LPMOs) are powerful enzymes that oxidatively cleave plant cell wall polysaccharides. LPMOs classified as fungal Auxiliary Activities family 9 (AA9) have been mainly studied for their activity towards cellulose; however, various members of this AA9 family have been also shown to oxidatively cleave hemicelluloses, in particularly xyloglucan (XG). So far, it has not been studied in detail how various AA9 LPMOs act in XG degradation, and in particular, how the mode-of-action relates to the structural configuration of these LPMOs.

RESULTS

Two Neurospora crassa (Nc) LPMOs were found to represent different mode-of-action towards XG. Interestingly, the configuration of active site segments of these LPMOs differed as well, with a shorter Segment 1 (^-Seg1) and a longer Segment 2 (⁺Seg2) present in NcLPMO9C and the opposite for NcLPMO9M (⁺Seg1^-Seg2). We confirmed that NcLPMO9C cleaved the non-reducing end of unbranched glucosyl residues within XG via the oxidation of the C4-carbon. In contrast, we found that the oxidative cleavage of the XG backbone by NcLPMO9M occurred next to both unbranched and substituted glucosyl residues. The latter are decorated with xylosyl, xylosyl-galactosyl and xylosyl-galactosyl-fucosyl units. The relationship between active site segments and the mode-of-action of these NcLPMOs was rationalized by a structure-based phylogenetic analysis of fungal AA9 LPMOs. LPMOs with a ^-Seg1⁺Seg2 configuration clustered together and appear to have a similar XG substitution-intolerant cleavage pattern. LPMOs with the ⁺Seg1^-Seg2 configuration also clustered together and are reported to display a XG substitution-tolerant cleavage pattern. A third cluster contained LPMOs with a ^-Seg1^-Seg2 configuration and no oxidative XG activity.

CONCLUSIONS

The detailed characterization of XG degradation products released by LPMOs reveal a correlation between the configuration of active site segments and mode-of-action of LPMOs. In particular, oxidative XG-active LPMOs, which are tolerant and intolerant to XG substitutions are structurally and phylogenetically distinguished from XG-inactive LPMOs. This study contributes to a better understanding of the structure-function relationship of AA9 LPMOs.

Iron-polyphenol complexes cause blackening upon grinding Hermetia illucens (black soldier fly) larvae

Insects are a promising alternative protein source. One of the bottlenecks in applying insects in food is the fast darkening initiated during grinding. Besides enzymatic browning, non-enzymatic factors can cause off-colour formation, which differs between species. This study investigates the impact of iron, phenoloxidase, and polyphenols on off-colour formation in insect larvae. Hermetia illucens showed a blackish colour, whereas Tenebrio molitor turned brown and Alphitobius diaperinus remained the lightest. This off-colour formation appeared correlated with the iron content in the larvae, which was 61 ± 9.71, 54 ± 1.72 and 221 ± 6.07 mg/kg dw for T. molitor, A. diaperinus and H. illucens, respectively. In model systems, the formation of iron-L-3,4-dihydroxyphenylalanine (L-DOPA) bis- and tris-complexes were evidenced by direct injection into ESI-TOF-MS, based on their charges combined with iron isotope patterns. The reversibility of the binding of iron to phenolics, and thereby loss of blackening, was confirmed by EDTA addition. Besides complex formation, oxidation of L-DOPA by redox reactions with iron occurred mainly at low pH, whereas auto-oxidation of L-DOPA mainly occurred at pH 10. Tyrosinase (i.e. phenoloxidase) activity did not change complex formation. The similarity in off-colour formation between the model system and insects indicated an important role for iron-phenolic complexation in blackening.

Effect of soybean processing on content and bioaccessibility of folate, vitamin B12 and isoflavones in tofu and tempe

PURPOSE

To compare the content of bioaccessible folate, vitamin B12, and isoflavones in tofu and tempe, as influenced by soybean variety and food processing, particularly fermentation.

PRINCIPAL RESULTS

Raw soybeans contained 2207-2671 μg/kg (dry matter) folate, cooked tempe 1493-4143, and cooked tofu 968-1273 μg/kg, the difference was attributed to the fermentation in tempe. Vitamin B12 was detected only in tempe (0.16-0.72 μg/kg). Isoflavone aglycones were formed during soaking of soybeans, with only minor differences between the contents in cooked tempe (average 1922-2968 μg/kg) or tofu (1667-2782 μg/kg) but strongly depending on bean variety.

CONCLUSIONS

Folate and vitamin B12 contents were mainly influenced by microbial activity during fermentation, whereas isoflavone aglycone content was determined by bean variety. Tofu had lower folate and vitamin B12, but equal isoflavone contents as tempe. Bioaccessibility of folate (80-100%) and isoflavone aglycones (100%) were high.

The impact of exercise on body composition and nutritional intake in patients with heart failure

Little is known about the nutritional status of heart failure patients and the potential synergistic effects between nutritional intake and exercise. This small, randomized trial examined the effects of a 3-month exercise program on body composition and nutritional intake in 31 men (17 exercisers; 14 controls), aged 30-76 years (mean, 56 years) with stable class II-III heart failure. Baseline and 3-month evaluations included body mass index, body fat mass by triceps skinfold thickness, dietary intake by food frequency questionnaire, and the 6-minute walk test. Exercise consisted of walking 3 d/wk and resistance exercises 2 d/wk for 40-60 minutes. Dietary recommendations were consistent with the American Heart Association/American College of Cardiology heart failure guidelines. Exercisers decreased body weight (p=0.001), body mass index (p=0.0001), and triceps skinfold thickness (p=0.03) and improved 6-minute walk test (p=0.01) compared with controls. Exercisers also demonstrated trends toward decreased total caloric and cholesterol intake and a three-fold higher carbohydrate, fiber, and beta carotene intake vs. controls. In this study population, protein, fiber, and magnesium intake were below recommended daily allowance. After exercise, body mass index was reduced, accompanied by dietary modifications including greater intake of foods with higher moisture content. Further study is needed to investigate the interaction among diet, exercise, and weight.

Performance of copper naphthenate and its analogs as ground contact wood preservatives

For several years, an extensive research program investigating new preservative systems has been ongoing at Mississippi State University. This paper details our continuing experience with field testing of copper naphthenate and other copper carboxylate preservative systems. Results from field stake tests at an AWPA Zone 4 test site are presented. In general, copper carboxylates made with 'synthetic' acids yielded results equivalent to or only slightly lower than systems with straight naphthenic acids or nap acids amended with synthetic neodecanoic acid bottoms. Oil carrier formulations outperformed those in water or light organic solvents. All systems carried in oil would qualify as ground contact preservatives at the proper retention.

The impact of type 2 diabetes and peripheral arterial disease on quality of life

Peripheral arterial disease (PAD) is associated with impaired walking distance as the result of claudication and reduced quality of life (QOL). Diabetes mellitus (DM) is commonly associated with PAD. The combined effect of DM and PAD versus PAD alone on walking distance and QOL is not well understood. This prospective, descriptive study examined walking distance and QOL associated with DM and PAD compared with PAD alone. Walking distance was assessed by an exercise treadmill test to determine initial claudication distance and absolute claudication distance and by self-report using the Walking Impairment Questionnaire. QOL was measured using the Short Form-36. The overall sample consisted of 92 men and women with PAD and DM or PAD alone. Of the total sample, 74 participants had PAD with ABI less than 0.9 mm Hg and 18 subjects had PAD and uncontrolled DM with hemoglobin A1c 7.0 mg/dL or greater. The mean age was 72 years (standard deviation [SD] = 7) for the PAD only group and 75 years (SD = 8) (not significant) for the PAD and DM groups. Initial claudication distance was greater in subjects with PAD only (186.9 m, SD = 136.4) than in diabetic subjects with PAD (127.3 m, SD = 70.0, P = .01). Absolute claudication distance was higher in patients with PAD only (461.3 m, SD 308) than in diabetic subjects with PAD (279.1 m, SD = 100, P = .01). Self-reported walking speed was reduced in patients with DM and PAD compared with patients with PAD only (P = .05). Diabetic patients with PAD reported impaired role function (P = .007), general health (P = .03), and social function (P = .04) compared with patients with PAD only. We conclude that DM has a significant detrimental impact on walking distance and QOL in patients with PAD. These findings suggest that diabetic patients with PAD are at greater risk for experiencing social isolation, impaired role function, reduced overall perceptions of general health, and impaired functional capacity. Future studies with larger sample sizes are needed to identify factors that contribute to these perceptions in diabetic patients with PAD.

Trehalose degradation and glucose efflux precede cell ejection during germination of heat-resistant ascospores of Talaromyces macrosporus

Talaromyces macrosporus forms ascospores that survive pasteurization treatments. Ascospores were dense (1.3 g ml(-1)), relatively dry [0.6 g H(2)O (g dry weight)(-1)] and packed with trehalose (9-17% fresh weight). Trehalose was degraded to glucose monomers between 30 and 100 min after heat activation of the spores. The maximal activity of trehalase was calculated as 400-520 nmol glucose formed min(-1) (mg protein)(-1) as judged by measurements of the trehalose content of spores during germination. During early germination, glucose was released from the cell (10% of the cell weight or more). The intracellular concentration of glucose only peaked briefly. After 160-200 min, the protoplast encompassed by the inner cell wall was ejected through the outer cell wall in a very quick process. Subsequently, respiration of spores increased strongly. The data suggested that trehalose is primarily present for the protection of cell components as glucose is released from the cell. Then, an impenetrable outer cell wall is shed before metabolic activity increases.

Analytical applications of liquid phase chemiluminescence reactions--a review

This paper reviews the literature on analytical applications of quantitative liquid phase chemiluminescence (CL) from 1991 to mid-1995. Other relevant reviews in this general area are also cited to provide an historical perspective. The focus is on the two major analytical techniques used in conjunction with flow-through CL detection, namely flow injection (FI) and liquid chromatography (LC). Entries have been tabulated under these two headings and are categorized in terms of the analyte, CL reaction, sample matrix and limits of detection.

Adaptive plasticity in primate spinal stretch reflex: persistence

Monkeys can gradually change the amplitude of the wholly segmental, largely monosynaptic, spinal stretch reflex (SSR) when confronted by a task requiring such change (15-19). Change develops over months and may reverse and redevelop at similarly slow rates. We investigated the persistence of SSR amplitude change over nonperformance periods of up to 38 days. Eight animals with chronic EMG electrodes learned to maintain elbow angle and a given level of biceps background EMG against constant extension torque. At random times, a brief additional extension torque pulse elicited the biceps SSR. In the control mode, reward always followed. Under the SSR increase or SSR decrease mode, reward occurred only if the absolute value of biceps EMG in the SSR interval was above or below a set value. Animals completed 3,000-6,000 trials/day over data-collection periods of 2-17 mo. Animals worked first under the control mode for up to 60 days and then under the SSR increase or SSR decrease mode for up to 274 days. Mode was switched once or twice more (SSR increase to SSR decrease or vice versa) over subsequent months. Animals responded to each SSR increase or SSR decrease mode exposure with gradual mode-appropriate change in SSR amplitude. Mode exposures were interrupted by gaps in performance of 10-38 days. Gaps produced transient 10- to 15% decreases in SSR amplitude under the control mode. This nonspecific decrease disappeared over the first week of postgap performance. Under the control mode, gaps had no other effects on SSR amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced day-to-day variation accompanies adaptive plasticity in the primate spinal stretch reflex

Monkeys can change the amplitude of the spinal stretch reflex (SSR), or M1, when reward is made contingent on amplitude. The present study demonstrates that reduced SSR day-to-day variation accompanies such adaptive SSR change. This finding supports the assumption that initial, phase I, SSR change results from contingency-appropriate stabilization of tonic activity in relevant descending spinal cord pathways.

Adaptive plasticity in the spinal stretch reflex

Monkeys can change the amplitude of the spinal stretch reflex without change in initial alpha motor neuron tone, as measured by EMG, or in initial muscle length. Change is apparent in 5-10 days, continues to develop over weeks, and persists during inactive periods. Spinal stretch reflex change may be a valuable system for studying the neuronal and synaptic bases of an adaptive change in primate CNS function.

Changes in the U.S. Army aviator selection and training program

The Army's aviator selection program began in the mid 1950's. The first Flight Aptitude Selection Test (FAST) was implemented in 1966 and remained in use until 1980 when changes in personnel, aircraft, and tactics necessitated an improved or revised FAST (RFAST). This paper presents an overview of 1) the composition of the FAST and RFAST; 2) the advantages of the RFAST; and 3) the predictive validity estimates for the FAST and RFAST. Also presented are examples of current research projects which show promise for increasing effectiveness and for broadening the scope of the Army aviator selection program.

A human performance/workload evaluation of the AN/PVS-5 bifocal night vision goggles

Eight experienced U.S. Army aviators performed various maneuvers in an instrumented helicopter to test the relative usability of two bifocal-configured night vision goggles. Both configurations were statistically better than the unmodified arrangement when looking at a pilot's ability to fly a standard traffic pattern and to hold a precise altitude at night. The subjective data, supported by comparative flight performances with the two bifocals, further suggested that a 24% bifocal version was more desirable than a 14% configuration. The inference is that the reduced inside field of view presented by the 14% bifocal interferes with a pilot's ability to readily locate instruments once he has directed his attention inside the cockpit.

Marijuana and human performance: an annotated bibliography (1970-1975)

A bibliography of 199 annotated references was compiled to aid the reader in determining the impact of marijuana on psychomotor, cognitive, and physiological factors considered pertinent to flight performance. The bibliography contains an index which categorizes the references into the following major areas: (1) reviews or overviews of issues, literature or research; (2) psychological effects of marijuana use; (3) physiological and pharmacological research; (4) medical comments and research critiques; and (5) additional reference sources. The basic period of coverage is 1970 to 1975, although selected studies from earlier years are also included.

Internal-external locus of control and performance on a vigilance task

Previous studies have demonstrated there are large individual differences in subjects' ability to perform on vigilance or watch-keeping tasks. This study used Rotter's Internal-External (I-E) Locus of Control Scale to resolve some of the variance attributed to individual differences and tested the hypothesis that the internally controlled person is a better monitor on a vigilance task than an externally controlled person. There were 64 subjects who performed a visual watch-keeping task for a 1-hr. period. The results indicated that the external subjects made significantly more incorrect responses and missed significantly more signals during the entire task. The internal-external dimension was effective in differentiating performance on a vigilance task.

Cross-validation study of the personality aspects of involvement in pilot-error accidents

Pilot-error accidents have dominated accident statistics consistently from the 1940s to the present. Sanders and Hofmann (3) found that three factors from Cattell's Sixteen Personality Factor Questionnaire (16 PF) significant differences (p less than 0.05) between pilot-error accident groups and were used to correctly classify 86% of the aviators tested as to their previous pilot-error accident involvement. There were 66 aviators given the 16 PF in the present study in an attempt to cross-validate the findings reported in the original study. The results indicate that the personality factors did not significantly discriminate between the pilot-error accident groups. The primary personality differences between the present sample and the original sample were due to variations in the pilot-error accident-free groups. The findings indicate that individual differences in personality characterstics of the aviators prevent consistent identification of traits associated with pilot-error groups.

Personality aspects of involvement in pilot-error accidents

The consistently high frequency of pilot-error accidents in both military and civilian aviation programs does much to support exploratory research which might help alleviate the problem. Cattell's Sixteen Personality Factor Questionnaire (16 PF), Mehrabian Achievement Scale, and a dynamic decision making task (under risk) were given to 51 Army aviators. Accident files were then examined in order to classify the aviators as to their prior pilot-error accident involvement. Stepwise discriminant analyses revealed that the decision-making task scores and the achievement scores were unrelated to the pilot error accident groupings while the 16 PF scores were able to correctly classify 86% of the aviators as to whether or not they had been previously listed as a cause factor in a military aviation accident.

Attenuation of "acute" habituation by scopolamine in the black-tailed prairie dog (Cynomys ludovicianus)

The hypothesis after scopolamine attenuates habituation occurring within a training session as well as that occurring between training sessions was tested and confirmed. Scopolamine injections (.5 mg/kg) reduced spontaneous wheel running in the prairie dog. The same dosage did not affect the threshold for wheen running induced by electrical brain stimulation (EBS). Another experiment demonstrated that EBS-induced running declined during a 10-min. stimulation period and indicated that the decline was habituative since the response was repeatedly dishabituated. In a final experiment .5 mg/kg of scopolamine reduced habituation of EBS-induced wheel running during 10-min. sessions.

Chronic idiopathic intestinal pseudo-obstruction with malabsorption, a scleroderma-like disorder

A case of intestinal pseudo-obstruction in a 76-year-old man who presented with a six-year history of intermittent vomiting and abdominal pain and a 1(1/2)-year history of diarrhea is described. Investigation demonstrated aperistalsis of the lower esophagus and an unresponsive atonic small intestine. Marked malabsorption was present and appeared due to intestinal bacterial overgrowth consequent to the hypomotility. Autonomic nervous system testing failed to reveal any definite abnormality. Although this disorder is markedly similar to scleroderma involving the gastrointestinal tract, there was only minimal fibrosis of the bowel musculature evident at autopsy and the neural components appeared to be intact. These findings suggest that the basic disorder may be one of smooth muscle dysfunction. Other known causes of pseudo-obstruction could not be demonstrated.

Hepatic abscess caused by Salmonella paratyphi B

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