Bacterial Spoilage of Thawed Frozen Peas

The main groups of bacteria developing in peas were isolated on differential media. Leuconostoc mesenteroides and Streptococcus lactis predominated and smaller numbers of catalase positive 'coryneform'bacteria were also regularly present. Strep. cremoris , streptococci (group D), catalase positive cocci and Gram negative rods were less regularly isolated.
Bacterial spoilage of untreated peas was usually accompanied by the development of a yellow colour and a reduction in pH. In pure culture in peas leuconostocs and group N streptococci produced an acid pH while the catalase positive organisms produced alkali, sometimes with ammoniacal odours. In mixed cultures in peas the products of a leuconostoc and a 'coryneform'tended to neutralize each other. A leuconostoc and a 'coryneform'did not interfere with each others'growth when grown from similar inocula. The behaviour of streptococci is still being investigated. The type and rate of spoilage probably depends on the balance between ammonia production and acid production in the system.     

THE BIOLOGICAL OXIDATION OF SPENT GAS LIQUOR

SUMMARY: Mixed cultures of bacteria grown in spent gas liquor readily oxidized phenol, o -, m - and p -cresol, catechol, 3-methyl catechol, 4-methyl catechol, resorcinol, 2-methyl resorcinol, and 4-methyl resorcinol. Quinol, pyrogallol and phloroglucinol were more resistant. The optimum temperature was 30° and the best pH range 6·5–7·8. Yeast extract and sterile sewage sludge both increased the rate of growth of organisms in liquor when the inoculum was small. Five phenol oxidizing organisms were isolated in pure culture. Copper in concentrations greater than 1 p/m inhibited both growth and phenol oxidation by one of these.
Mixed cultures grown in an ammonium thiocyanate medium originally inoculated with Thiobacillus thiocyanoxidans oxidized potassium thiocyanate and sodium thiosulphate. Chloride inhibited thiocyanate oxidation in concentrations above 5,000 p/m, although adaptation to 15,000 p/m was possible. Phenol inhibited thiocyanate oxidation in concentrations of 300 p/m or more. Mixed cultures grown on sodium thiosulphate oxidized sodium trithionate and tetrathionate, potassium pentathionate and hexa-thionate, and potassium and ammonium thiocyanate
Manometric determinations of the 5 day biological oxygen demand of effluents after treatment showed good agreement with the values obtained by the conventional method, the manometric values being usually somewhat higher.     

The significance of flower colour change in eight co-occurring shrub species

Flower colour changes from white or yellow to various shades of red at or near the sites of harvestable pollen in Calytrix glutinosa, Grevillea pilulifera, Isopogon dubius and Petrophile biloba , and over most of the flower in Hypocalymma angustifolium, Verticordia chrysantha and V. huegelii and over the pseudanthium in Darwinia citriodora. All bee, wasp, beetle, fly, butterfly and moth visitors select flowers in the white/yellow phase rather than the red or intermediate phase.
Nectar is produced by five species, harvestable pollen by four species and detectable perfume by three species, all of which features are usually absent from the red phase. The timing of the colour change in all species also corresponds to loss of stigma receptivity, completion of pollination and onset of ovule seed) swelling. Six species also undergo minor morphometric changes which discourage visitation. In all species, colour change is non-inducible by pollinators, taking 2–30 days to complete. In three protandrous species, all available pollen may be removed in the first visit, requiring transport of non-self pollen to rewardless flowers during the 10 h period of the yellow phase.
These species are highly floriferous and occur in dense patches. Since only a small proportion of flowers may be receptive at any one time, it is concluded that retention of flower parts essentially serves to enhance long-distance attraction, while colour change maximizes pollination and foraging efficiency.     

Improved 18-Hour Methyl Red Test

Standard methods for the methyl red (MR) test are not practical for routine use in clinical laboratories because of the necessarily prolonged incubation period. When read after overnight incubation, the usual MR test is often equivocal or falsely positive. The present study demonstrates the importance of standardizing the total volume of broth, the size of the vessel in which the cultures are incubated, and the density of the inoculum. In very small volumes of broth, cultures are better exposed to atmospheric oxygen, and thus MR-negative organisms tend to revert the initial acidic pH much more quickly than in deeper, large-volume broth cultures. In the proposed technique, a single colony was inoculated into a 0.5-ml amount of MR-Voges Proskauer (VP) broth (13- by 100-mm tube), and, after 18 to 24 hr at 37 C, one drop of MR was added. With this technique, the broth cultures produced either a definite red (positive) or yellow (negative) color, whereas various shades of orange were frequently observed when larger volumes of broth were tested after only 1 to 2 days of incubation. With 6.0-ml broth cultures, 18-hr MR tests were totally unreliable, but 18-hr tests in 0.5 ml of broth were comparable to the standard MR test performed after 5 days of incubation and superior to those performed after 48 hr in 6.0-ml broth cultures. With the proposed technique, the MR test can be incorporated readily into the routine scheme for identification of Enterobacteriaceae.     

Demethylation of Veratrole by Cytochrome P-450 in Streptomyces setonii

The actinomycete Streptomyces setonii 75Vi2 demethylates vanillic acid and guaiacol to protocatechuic acid and catechol, respectively, and then metabolizes the products by the β-ketoadipate pathway. UV spectroscopy showed that this strain could also metabolize veratrole (1,2-dimethoxybenzene). When grown in veratrole-containing media supplemented with 2,2′-dipyridyl to inhibit cleavage of the aromatic ring, S. setonii accumulated catechol, which was detected by both liquid chromatography and gas chromatography. Reduced cell extracts from veratrole-grown cultures, but not sodium succinate-grown cultures, produced a carbon monoxide difference spectrum with a peak at 450 nm that indicated the presence of soluble cytochrome P-450. Addition of veratrole or guaiacol to oxidized cell extracts from veratrole-grown cultures produced difference spectra that indicated that these compounds were substrates for cytochrome P-450. My results suggest that S. setonii produces a cytochrome P-450 that is involved in the demethylation of veratrole and guaiacol to catechol, which is then catabolized by the β-ketoadipate pathway.     

Shell colour variation in Littorina saxatilis Olivi (Prosobranchia: Littorinidae): a multi-factor approach

The marine snail Littorina saxatilis is highly polymorphic for shell colour. It lives in the heterogeneous intertidal zone, where there are sharp transitions in a number of abiotic factors that may influence the relative fitness of morphs. We investigated the hypothesis of selected variation by relating the colour distribution to five factors (wave exposure, substratum, shore level, sex, snail age), and to interactions between them. We compared patterns from geographical areas in Sweden, Iceland and Russia. Cryptic morphs (tessellated and different dark colours) generally dominated (80–98%) while conspicuous morphs (white, yellow, red and banded) were less common (2–20%). The colour frequencies were often related to wave exposure, substratum and shore level. Frequencies rarely varied with age and never with sex. In order to test the assumption that the different colours are genetically determined we cross-bred snails from Iceland in the laboratory. Both the presence of bands and the ground colours of the shell were inherited, and we have tentative support for a one-locus two-allele model for banding. Our results support a model of selected inherited colour variation, involving a number of different selective agents, the importance of which may vary between populations on local and geographical scales.     

Development and application of a simple filter paper imprinting technique for the detection and enumeration of colonies of ureolytic micro-organisms

A rapid, simple and inexpensive method has been devised to determine the proportion of colonies of ureolytic organisms in cultures of complex microbial populations. Spiral plated cultures displaying well separated colonies are tested for ureolytic micro-organisms by imprinting the colonies onto filter papers impregnated with a solution of 1 mol/l urea and phenol red (0·1% w/v) in 0·1 mol/l phosphate buffer (pH 6·8). A rapid colour change indicates ureolytic activity. The proportion of ureolytic colony-forming units in cultures of saliva specimens from 90 school children ranged from less than 1% to 40% (mean 9·9%± 7·7). Saliva and dental plaque specimens from 16 adult subjects were also tested and the occurrence of urease-positive organisms was substantially less in plaque (3·6%± 3·7, range 0·1–12) than saliva (18·7%± 13·8, range 1·3–51). The predominant ureolytic oral species was Streptococcus salivarius , 75 (54·7%) of 137 tested isolates being urease-positive.     

Biodegradation of chrysene by the bacterial strains isolated from oily sludge

The biodegradation studies were conducted to test the ability of the bacterial strains (Chry2 and Chry3) isolated from the oily sludge obtained from Gujarat refinery, India, for utilization of chrysene in the liquid medium. Biodegradation of the compound was confirmed using gas chromatography and the percent degradation was calculated to be 15.0 and 17% by Chry2 and Chry3, respectively. The biodegradation results were supported by increase in viable cell count and dry biomass, in the presence of chrysene as the sole carbon source. Both the cultures produced biosurfactant which was indicated by the reduction in surface tension of the growth medium. Presence of catechol 2, 3-dioxygenase gene in Chry3 indicated its potential for degradation of PAHs through meta cleavage degradation pathway. Both the strains were found to possess catechol 1,2-dioxygenase and catechol 2,3-dioxygenase enzyme activities. Based on morphological and biochemical tests, the cultures were tentatively identified as Bacillus sp. (Chry2) and Pseudomonas sp. (Chry3).     

A Matter of Contrast: Yellow Flower Colour Constrains Style Length in Crocus species

Most flowers display distinct colour patterns comprising two different areas. The peripheral large-area component of floral colour patterns attracts flower visitors from some distance and the central small-area component guides flower visitors towards landing sites. Whereas the peripheral colour is largely variable among species, the central colour, produced mostly by anthers and pollen or pollen mimicking floral guides, is predominantly yellow and UV-absorbing. This holds also for yellow flowers that regularly display a UV bull’s eye pattern. Here we show that yellow-flowering Crocus species are a noticeable exception, since yellow-flowering Crocus species–being entirely UV-absorbing–exhibit low colour contrast between yellow reproductive organs and yellow tepals. The elongated yellow or orange-yellow style of Crocus flowers is a stamen-mimicking structure promoting cross-pollination by facilitating flower visitors’ contact with the apical stigma before the flower visitors are touching the anthers. Since Crocus species possess either yellow, violet or white tepals, the colour contrast between the stamen-mimicking style and the tepals varies among species. In this study comprising 106 Crocus species, it was tested whether the style length of Crocus flowers is dependent on the corolla colour. The results show that members of the genus Crocus with yellow tepals have evolved independently up to twelve times in the genus Crocus and that yellow-flowering Crocus species possess shorter styles as compared to violet- and white-flowering ones. The manipulation of flower visitors by anther-mimicking elongated styles in Crocus flowers is discussed.     

A colorimetric method for assay of serotonin deamination by monoamine oxidase

The present method involves conversion of the aldehyde produced, as a result of serotonin deamination by monoamine oxidase, to its 2:4 dinitrophenyl hydrazone derivative which gives a stable, bright yellow colour in alkaline solution and can be measured colorimetrically. The derivative is however unstable in the acidic medium and has to be extracted into an organic solvent immediately. The details of the method and its standardization are discussed.     

Dietary conservatism may facilitate the initial evolution of aposematism

It has generally been assumed that warningly coloured organisms pay a cost associated with their increased visibility, because naïve predators notice and eat them. This cost is offset by their enhanced protection from educated predators who associate the colour pattern with unprofitability. However, some studies have suggested that avoidance of novel prey by avian predators ("dietary conservatism") can actually place novel colour morphs at a selective advantage over familiar ones, even when they are highly conspicuous. To test this idea, we experimentally simulated the appearance of a single novel-coloured mutant in small populations (20 individuals) of palatable artificial prey. The colour morph frequencies in each "generation" were determined by the relative survival of the previous generation under predation by birds. We used wild-caught European robins Erithacus rubecula foraging on pastry "prey" of different colours. The aim was to test whether prey selection by predators prevented or facilitated the novel colour morph persisting in the prey population over successive generations. We found that the novel colour morph quickly increased to fixation in 14/40 prey "populations", and at least once each in 8 of the 10 birds tested. Novel mutants of the classic aposematic colours (red and yellow) reached fixation most frequently, but even the green and blue novel morphs both increased to fixation in 2/40 trials. Novel colours reached fixation significantly faster than could be accounted for by drift, indicating active avoidance by the birds. These results suggest that a novel colour morph arising in a prey population can persist and increase under the selective pressure imposed by predators, even to the local exclusion of the original morph, despite being fully palatable. The consequences of this finding are discussed in relation to receiver psychology, the evolution of aposematism and the existence of polymorphism in Müllerian mimics.     

Encephalitozoon-Like Organisms in Patients with Alveolar Hydatid Disease: Cell Culture, Ultrastructure, Histoimmunochemical Localization and Seroprevalence

ABSTRACT. We found Encephalitozoon -like organisms in an in vitro culture of a human liver lesion which was due to larval Echinococcus multilocularis. The organisms developed in the same fashion as an Encephalitozoon cunculi. The spores that developed in parasitophorous vacuoles were 2.0–2.6 × 1.1–1.5 μm: each contained a single nucleus and 4–5 polar tubule coils, closely resembling E. cuniculi in its ultrastructure. Mature spores were collected from the supernatants by the use of Percoll centrifugation resulting in the banding of the spores on continuous gradients. We prepared three sorts of spores which were different in buoyant density in 0.15 M NaCl: 1.05–1.07 g/ml spores, 1.12 g/ml spores, and spores of over 1.14 g/ml. Polyclonal antibodies to a pool of each spore preparation were produced in a rabbit and applied to the detection of microsporidian antigen in situ. The histoimmunoperoxidase (HIP) procedure was used to detect the microsporidian antigen in echinococcal liver lesions from patients with alveolar hydatid disease (AHD). Ten echinococcal liver lesions from different AHD patients were examined and four were found to be positive in the HIP test. The Percoll-separated spores were also used as an antigen to detect for antibodies in the sera from the patients with AHD by Western blotting. Antibodies were detected in 62 (52%) of the 119 AHD patients and in only 8 (5%) of the 159 normal healthy individuals.     

The major carotenoid pigments of the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae)

The economically important grain aphid, Sitobion avenae (F.) shows colour polymorphism, with brown and green forms predominating. Colour is determined both genetically and in response to environmental factors, including nutrition. The biological significance of the colour polymorphism is unknown, although seasonal changes occur in the frequency of colour morphs in the field, whilst the brown morph may have adaptive significance in terms of hymenopterous endoparasitism. The ground colour of aphids is produced by haemolymph pigments, aphins (glucosides) and carotenoids. The latter may be under the synthetic control of intracellular endosymbiotic bacteria. In this study, the major carotenoid pigments of a brown and a green clone of S. avenae were examined using thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC), and their absorbance spectra recorded. Using TLC, the brown clone produced five bands of different R_f, ranging from yellow, to orange-pink to pink in colour. In contrast, the green clone gave only a single yellow band of higher R_f than any of the bands of brown aphids. Following separation of carotenoids by HPLC, brown aphids gave seven peaks and green aphids five. Comparison of absorbance maxima with known published values for carotenoids provides strong evidence for the identification of four of the carotenoid pigments from brown aphids (RB-4, 3,4-didehydrolycopene; RB-5, torulene; RB-6; lycopene; RB-7, γ-carotene) and one from green aphids (RG-2, α-carotene). The other carotenoids remain unidentified. The biosynthesis and possible biological relevance of the various pigments of S. avenae are briefly discussed.     

Learning and discrimination of coloured papers in the walking blowfly,Lucilia cuprina

Summary A new training and testing paradigm for walking sheep blowflies, Lucilia cuprina, is described. A fly is trained by presenting it with a droplet of sugar solution on a patch of coloured paper. After having consumed the sugar droplet, the fly starts a systematic search. While searching, it is confronted with an array of colour marks consisting of four colours displayed on the test cardboard (Fig. 1). Colours used for training and test include blue, green, yellow, orange, red, white and black.Before training, naive flies are tested for their spontaneous colour preferences on the test array. Yellow is visited most frequently, green least frequently (Table 2). Spontaneous colour preferences do not simply depend on subjective brightness (Table 1).The flies trained to one of the colours prefer this colour significantly (Figs. 5 and 9–11). This behaviour reflects true learning rather than sensitisation (Figs. 6–7). The blue and yellow marks are learned easily and discriminated well (Figs. 5, 9, 11). White is also discriminated well, although the response frequencies are lower than to blue and yellow (Fig. 11). Green is discriminated from blue but weakly from yellow and orange (Figs. 5, 9, 10). Red is a stimulus as weak as black (Figs. 8, 9). These features of colour discrimination reflect the spectral loci of colours in the colour triangle (Fig. 14).The coloured papers seem to be discriminated mainly by the hue of colours (Fig. 12), but brightness may also be used to discriminate colour stimuli (Fig. 13).     

The use of immobilized lectins in the separation of Staphylococcus aureus, Escherichia coli, Listeria and Salmonella spp. from pure cultures and foods

Lectins from Helix pomatia, Canavalia ensiformis, Agaricus bisporus and Triticum vulgaris agglutinated cultures of Staphylococcus aureus, Escherichia coli, Listeria and Salmonella spp. This agglutination was specific as it was inhibited (except with A. bisporus lectin) by the competing sugar substrates. The ability of three of these lectins, immobilized on a variety of supports, to separate these micro-organisms from pure cultures was investigated. Immobilization of the lectins on magnetic microspheres was the most effective method. Immobilized T. vulgaris lectin bound 87–100% of cells from cultures of L. monocytogenes , 80–100% of Staph. aureus , 33–45% of Salmonella spp. and 42–77% of E. coli. The A. bisporus lectin bound 31–63% of cells in cultures of L. monocytogenes , 83% of Staph. aureus but only 3–5% of the salmonella cells. Similarly H. pomatia lectin bound >92% of Staph. aureus and 64% of L. monocytogenes cells but was poor at binding the Gram-negative organisms. This preference for binding Gram-positive organisms was confirmed when mixed cultures were studied. The T. vulgaris lectin was effective in removing L. monocytogenes (43%) and Staph. aureus (26%) from diluted milk and Salmonella (31–54%) from raw egg. Agaricus bisporus lectin removed L. monocytogenes from undiluted milk (10–47%) or ground beef (32–50%).     

Rapid evaluation of biocidal activity using a transposon-encoded catechol 2,3-dioxygenase from Pseudomonas putida

Pseudomonas putida (UWC1), containing a genetically-engineered plasmid (pQM899), that encodes for the production of catechol 2,3-dioxygenase (C230), was used as a potential means of rapidly estimating bactericidal activity of chlorhexidine diacetate (CHA), phenol, cetylpyridinium chloride (CPC) and phenylmercuric nitrate (PMN). Enzyme C230 converts catechol to 2-hydroxymuconic semialdehyde (2-HMS), which is yellow in colour, via a meta cleavage pathway. Ideal conditions for production and measurement spectrophotometrically of 2-HMS were determined. However, the correlation between this method and viable plate counts was not sufficiently accurate to enable 2-HMS production to provide a sufficiently sensitive determination of biocidal activity. An alternative method, synchronous scanning fluorimetry, in which the decrease in catechol concentration was measured under standardized conditions, provided a good dose-response histogram for all the biocides tested. Although, in comparison with plate counts, there was an underestimation of the bactericidal effects of phenol an PMN, the results of this study suggest that this method has potential in determining the bactericidal efficacy of agents such as CHA and CPC.     

Shell colour variation in Bullia digitalis, a sand-dwelling, intertidal whelk (Gastropoda: Prosobranchia)

Bullia digitalis is an intertidal whelk that lives on sandy beaches in South Africa. It is highly variable in shell colour, with individuals varying from white to dark brown. This paper describes shell colour variation of B. digitalis at seven sites, along a 230 km coastline east of the Cape Peninsula. Seven colour forms were found: striped, violet, banded violet, banded brown, orange, pale yellow and white. These forms are probably genetically determined morphs. The striped form is the most common at all sites, constituting 53–62% of each sample. The violet is the second most common morph. Its frequencies are remarkably stable at 15–17%. The striped form blends well into the sandy environment and may therefore be of considerable cryptic value in concealing B. digitalis from predators. The violet form is highly conspicuous. Its stable frequency throughout the study area may represent a genetic balance that is not relevant to any visual advantages of the violet colour.     

Visual cues and foraging choices: bee visits to floral colour phases in Alkanna orientalis (Boraginaceae)

When a pollination vector is required, any mechanism that contributes to floral visitation will potentially benefit the reproductive fitness of a plant. We studied the effect of floral colour change in the desert perennial Alkanna orientalis on the foraging behaviour of the solitary bee Anthophora pauperata . Flowers changed colour over time from bright yellow (with moderate nectar reward) to pale yellow/white (with significantly lower nectar reward). Bee visitation was non-random with respect to colour phase availability within the flower population and was biased towards the more rewarding flowers. At plants where the availability of colour phases had been manipulated experimentally to produce 'bright' or 'pale' plants, bees visited significantly more flowers (and for longer periods) on the bright plants. The change of flower colour was not simply age-related; we observed variation in the temporal course of colour change and our data suggest that visitation, leading to deposition of cross-pollen, can accelerate the process. In subpopulations with limited pollinators, Alkanna can influence bees by using their colour-related foraging preferences to alter visitation patterns.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 427–435.     

Colour discrimination by the sheep blowfly Lucilia sericata

Abstract. In laboratory trials designed to examine the alighting response of the blowfly Lucilia sericata Meigen to colour, yellow sticky cloth targets caught the largest number of both males and females, followed by pale blue, black, green, dark blue and red. The number caught by any colour showed a strong positive relationship with the percentage of its spectral reflectivity in the 450–580 nm wavelength band. In field trials, targets baited with the synthetic attractant 'swormlure' caught significantly fewer L.sericata than targets baited with liver and sodium sulphide, suggesting that the former bait is a relatively poor attractant for this species, at the release rates used in the present study. However, there was no effect of target colour on catch, neither was there any interaction between colour and odour bait type. The results, from both the laboratory and field trials, suggest that the strength of responses by Lsericata to visual cues are weak relative to responses to odour. Responses to hue are readily overridden by a range of factors such as brightness and contrast with the background and are therefore likely to be difficult to detect or manipulate reliably in trapping systems in the field.     

Histidine Decarboxylaseless Mutants of Lactobacillus 30a: Isolation and Growth Properties

Mutants of Lactobacillus 30a deficient in their ability to form an inducible histidine decarboxylase (EC 4.1.1.22) were selected by plating nitrosoguanidine-treated cultures on a medium containing histidine and methyl red. Wild-type organisms produce histamine, thus raising the pH and forming yellow colonies; mutant colonies remain red. In the presence of added histidine, decarboxylase-producing cultures grow more heavily than mutant cultures when the initial pH of the growth medium is low or when the lactic acid produced lowers the pH to growth-limiting values. Addition of the decarboxylation products, histamine and carbon dioxide, did not favor growth in crude medium.