Plasmids of Staphylococcus aureus associated with live and processed poultry

A series of 23 strains of Staphylococcus aureus originally isolated from processed poultry was screened for the presence of plasmids. Plasmids were more common in strains of Staph. aureus characteristically associated with live poultry than with strains endemic in poultry plants and strains of human origin. Two plasmids with sizes of 1·65 and 18·2 kilobase pairs (kBp) were present in three strains considered typical of Staph. aureus forma specialis 'altilis' and two plasmids with sizes of 1·65 and 17 kBp were present in three of four strains of Staph. aureus var. gallinae. A 1·65 kBp plasmid was present in all seven strains of these poultry biotypes and in three of 14 'endemic' strains. All the 1·65 kBp plasmids were shown by blot hybridization to share sequence homology. There was also some sequence homology between the 18·2 kBp and 17 kBp plasmids. These results were supported by restriction enzyme digest analyses. A study of cured derivatives of strain PS221 f.sp. 'altilis' suggested that the 18·2 kBp plasmid encoded the genetic determinant(s) responsible for caseolysis. Both the 1·65 and the 18·2 kBp plasmids also exerted an effect on the production of acid from lactose. In no other characteristic did cured strains resemble the plasmid-free 'endemic' strains. This was therefore consistent with the notion that the genetic determinants associated with the cultural characteristics of endemic strains are chromosomally located.     

Large plasmids in ruminal strains of Selenomonas ruminantium

The plasmid content of six different isolates of Selenomonas ruminantium from the rumen of sheep, cows or goats was examined by electron microscopy. In addition to small plasmids (< 12 kb) studied previously, all six strains contained at least one plasmid larger than 20 kb. Plasmid sizes of 1·4, 2·1, 2·4, 5·0, 6·2, 20·4, 20·8, 22·7, 23·3, 29·3, 30·7, 34·4 and 42·6 kb were estimated from contour length measurements. DNA-DNA hybridization experiments revealed homology among the large plasmids from five strains, while the 20·8 kb plasmid from a sixth isolate showed no apparent relationship with the plasmids of the other strains.     

Autotriploid tench Tinca tinca (L.) larvae obtained by fertilization of eggs previously subjected to postovulatory ageing in vitro and in vivo

Eggs of diploid tench Tinca tinca were half-stripped out and stored for 0 (control batch), 1, 3 and 5 h at mean ± s . d . 17·0 ± 0·4 and 21·9 ± 0·5° C or for 0, 1, 2, 3, 4 and 5 h at 24·0 ± 0·0° C in vitro prior to fertilization. The eggs remaining in vivo in the fish kept at 17·0 ± 0·4 and 21·9 ± 0·5° C were collected and fertilized in the same time intervals. Fertilization rate and larval yield mostly decreased after 3–5 h storage of eggs both in vitro and in vivo and only the diploid larvae were found in all control batches. Triploid larval yields increased to a maximum 5·26% after 5 h in vitro storage at 24·0° C and 1·07 and 1·60% after 3 h in vitro storage at 21·9 and 17·0° C, respectively. Triploid larval yield during in vivo storage at 21·9° C reached a maximum 0·91% after 5 h. As the spontaneous autotriploid larvae arose solely from fertilized eggs previously subjected to postovulatory egg ageing by means of prolongated storage, the autotriploidy was probably caused by failure of extrusion of the second polar body.     

Differential survival of juvenile sockeye and coho salmon exposed to low dissolved oxygen during winter

Juvenile sockeye salmon (43–78 mm) survived 100% for 24 h in cages in ice–covered Black Lake, Alaska at oxygen saturations >65% (9 mg l^–1), but only 45% at 24% saturation (3·0–3·3 mg l^–1) and none at <17% saturation (2·3 mg l^–1). All juvenile coho (50–120 mm) survived 100% for 24 h down to 21% oxygen saturation (3·1 mg l^–1), and all 50 coho survived 4–5 days at 23–24% saturation (3·2–3·3 mg l^–1).     

Description of Bacillus thuringiensis wratislaviensis (H-47), a new serotype originating from WrocŁaw (Poland), and other soil isolates from the same area

Twenty-four Bacillus thuringienis ( Bt ) strains were isolated and examined in respect of serotype, plasmid content crystal-composing proteins and insecticidal activity. Strains PO1–PO11 and PO14–PO15 were recognized as B. thuringiensis kurstaki H3a3b3c. The strains PO12 and PO13 were found to share a common novel antigen determining the new serotype H-47, and were designated as serovar wratislaviensis . Further investigations showed that all strains carried multiple plasmids (for example six different large plasmids in PO12 strain) and formed crystals composed of either two proteins, 135·8 kDa and 66·2 kDa (strains PO1–PO11 and PO14–PO24), or on protein, 66·2 kDa (strains PO12 and PO13). Preliminary toxicity tests with crude suspensions of spores and crystals showed rather low activity (<50% mortality) against fruitfly larvae and nymphs of cockroaches and high toxic effects (up to 90% mortality) against house fly larvae.     

Restriction analysis of plasmids of Bacillus thuringiensis subsp. israelensis H14

Restriction analysis of three small plasmids ( m _r; 3·65, 4·65 and 5·5 Md) of the mosquito pathogen Bacillus thuringiensis subsp. israelensis was performed. A restriction map of the 3–65 Md plasmid is presented. The stability of this plasmid, the availability of five single sites and the existence of a genetic transfer system make it ideal for development as a cloning vector.     

Distribution of plasmids in cyanobacteria of the LPP group

Abstract The distribution of plasmid DNA has been studied in 23 strains and variants of non-heterocystous filamentous cyanobacteria that are susceptible to infection by the LPP-1 cyanophage (archetype). 21 have identical plasmid profiles and contain 3 plasmids of M _rs 0.9, 10 and approx. 12 · 10⁶ respectively. In one strain, Plectonema FS180, the plasmids have been designated pMP1, pMP2, and pMP3, respectively. pMP1 shows sequence homology with pMP2 and pMP3 but not with DNA from an LPP-type cyanophage. Plectonema UTEX 598 lacks the small plasmid only, while Plectonema UTEX 1541 is distinct amongst all these strains with 3 plasmids of M _rs 3, 10, and > 30 · 10⁶, respectively. The findings support the view that the majority of these strains may be independent isolates of a single species.     

CELL PROLIFERATION IN THE CASTRATE MOUSE SEMINAL VESICLE IN RESPONSE TO TESTOSTERONE PROPIONATE

The cell proliferation kinetics following induced DNA synthesis in the mouse seminal vesicle were measured after treatment with testosterone propionate. Fraction labelled mitosis curves at 24, 48 and 72 hr after injection gave t ₂ values of 1·5, 2·0 and 1·8 hr respectively, and t _s values of 10·5, 8·0 and 8·0 hr. T _c measured 48 hr after stimulation was 17·5 hr. Growth fraction rose from 0·14 at 24 hr to 0·64 at 48 hr, and fell to 0·32 by 72 hr. A simple model is proposed in which the rise and fall of mitotic index and labelled index is determined by the 'cell distribution ratio'.     

Compensatory growth of juvenile brown flounder Paralichthys olivaceus (Temminck & Schlegel) following thermal manipulation

The compensatory growth of juvenile brown flounder Paralichthys olivaceus (body mass c. 12 g) following different thermal exposure was investigated. Fish were exposed to one of the five temperatures: 8·5 ( T _8·5), 13·0 ( T _13·0), 17·5 ( T _17·5), 22·0 ( T _22·0) and 26·5° C ( T _26·5) for 10 days and fish grew best at 22·0° C. Then the water temperature in all treatments was equably adjusted to 22·0° C over 3 days. At the end of the following 30 days after temperature adjustment, there were no significant differences between body masses of fish in the different treatments (wet body mass at the end of the experiment ranged from 22·13 to 24·56 g). Results indicated that the juvenile P. olivaceus achieved complete compensatory growth. Analysis of the dynamics of the feeding rates and feed conversion efficiencies indicated that compensatory growth of the fish experienced low temperature ( T _8·5, T _13·5 and T _17·5) or high temperature ( T _26·5) exposure was mainly dependent on increasing feed intake (hyperphagia) and possibly by improvement in feed conversion efficiency. The moisture content was not affected by different temperature exposure significantly. The lipid and energy content of juvenile P. olivaceus in T _8·5, however, were significantly lower than other treatment. Results of the current study indicate that a short period of low or high temperature exposure may not affect annual growth, but may affect lipid and energy deposition.     

Description of Careproctus patagonicus sp. nov. and C. magellanicus sp. nov. (Pisces: Scorpaeniformes) from the lower slope of Drake Passage

Two new species of Liparidae are described from Drake Passage (55°32·8' S, 65°54·3' W). Careproctus patagonicus differs from all other congeneric species in the following combination of characters: C 9 (1+4/4), epural and parhypural unfused to single hypural; gill slit above P base; lower pectoral lobe well developed; pectoral girdle with one ventral radial (0+0+0+1) with a central foramen; da 2·4, aAf 10·2% LS; disk 41·5% HL; some crater-like pits on posterior half of body; head and anterior part of body white. Careproctus magellanicus has the following diagnostic characters: A 46; P 24, well-developed lower pectoral lobe; scattered crater-like spots and some thumb-tack prickles on body; one suprabranchial pore; basal plate of the pectoral girdle with two fenestrae; four radials (3+1), the first with a ventral notch; HL 17·1, preD 18·5% LS. The structure of the endochondral pectoral girdle of both species is commented.     

Plasmid profiles of ten strains of Lactobacillus plantarum

Abstract The presence of extrachromosomal DNA elements has been investigated in 10 strains of Lactobacillus plantarum .
8 of the strains contained from 1 to 6 plasmids of different M _r values spanning from 1.35 · 10⁶ to 15.4 · 10⁶.
6 of the strains are commonly used as starter cultures in dry sausage and all these strains contained plasmids. The remaining 4 strains were obtained from the American Type Culture Collection and only 2 of these strains were found to harbour plasmids.     

Stress-induced changes in concentrations of plasma sex steroids in black bream

Cortisol levels of black bream Acanthopagrus butcheri at capture did not change with time of day, gonadal stage or season and were 1·9±0·2 and 2·8±0·4 ng ml⁻¹ for male and female fish, respectively. Confinement resulted in significantly elevated cortisol levels at all time periods; however, levels after 24 h of confinement were significantly lower than peak cortisol levels (15 min for males and 1 h for females). Confinement stress resulted in reduced levels of 17β-oestradiol (E2) and testosterone (T) within 1 h in sexually mature females. In mature males, suppression of T and 11-ketotestosterone (11KT) occurred after 30 min and 6 h of confinement, respectively. The relationship between confinement stress and levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20β P) was more complex, with levels in males being elevated after 15 min and 24 h and suppressed after 6 h of confinement. In contrast, 17, 20β P levels in females were elevated after 1 h of confinement. In regressed females, plasma E₂ and T concentrations were low at capture and were not affected by confinement stress whereas plasma 17, 20β P was elevated within 1 h. This study indicates that stress exerts a rapid inhibitory effect on gonadal steroidogenesis.     

Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.     

BIOSYNTHESIS OF PSYCHOSINE AND LEVELS OF CEREBROSIDES IN THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS OF QUAKING MICE

Abstract— The levels of cerebrosides in neural tissues of adult mice were determined by densitometry of cerebroside spots on charred thin-layer chromatograms of washed total lipid extracts. Values for brain, spinal cord and peripheral nerves were 9·2, 33·0 and 36·9 mg/g of tissue, respectively. In adult Quaking mice these values were 6·4, 24 and 35 % of normal, respectively. Normal levels in brain, spinal cord and peripheral nerve of 21-day-old mice were 3·10, 13·5 and 17·8 mg/g, respectively. In 21-day-old Quaking mice the levels were reduced to 16,21 and 57% of normal, respectively. Biosynthesis of psychosine (galacto-sylsphingosine) by homogenates of Quaking brain, spinal cord and peripheral nerve, respectively, was 18, 24 and 42% of the normal rates at 21 days after birth and 16, 66 and 60% of the normal rates at 94 days. Our results suggest a quantitative relationship between the rate of formation of psychosine in vitro and the rate of accumulation of cerebrosides. in vivo. Biosynthesis of lactosylceramide was not reduced in homogenates of brain and spinal cord from Quaking mice. Cerebroside levels in normal and Quaking spinal cord and in normal brain increased 2- to 3-fold after 21 days of age, but in Quaking brain there was little or no increase.     

A medium density microsatellite map of BTA10: reassignment of INRA69

We have developed a genetic map of BTA10 based on 8952 informative meioses for 13 microsatellite markers and the erythrocyte antigen Z. With the exception of OarAE64 , the support for the order of all loci in the map exceeded a LOD > 3·0. The length of the BTA10 genetic map was 87·0 centimorgans (cM). The 14-marker, sex-average map in Kosambi cM was: CSSM38 –8·9- BM1237 –5·2- HH8A –2·6- INRA69 –10·6- TGLA378 –0·8- BM6305 –17·2- TGLA102 –17·9- INRA96 –0·3- CSRM60 –9·2- DIK20 –3·0- EAZ –6·7- CSSM46 –3·7- SRCRSP3 –1·0- OarAE64 with an average interval of 6·70 cM. The microsatellite INRA69 was recently assigned to the pseudoautosomal region of the bovine X chromosome by linkage analysis. However, we found that twopoint support for linkage between INRA69 and 15 X-linked bovine microsatellites was LOD < 0·50 in 529 reciprocal backcross and F₂ fullsib progeny. We performed twopoint analyses of INRA69 against 275 markers distributed throughout the bovine genome and found significant associations with a LOD > 3·0 only between INRA69 and eight BTA10 microsatellite loci. Consequently, we excluded INRA69 from the genetic map of the X chromosome and reassign this microsatellite to BTA10.     

Mini-chromosomes: plasmids which carry the E. coli replication origin.

Summary We have isolated plasmids by linking the 5.9 MD EcoRI fragment of E. coli that carries the origin of replication to an EcoRI fragment that carries an ampicillin resistance determinant, but lacks an origin of replication. 3 plasmids of this type, pOC1, pOC2, and pOC3, are described in detail in this report. Although the plasmids have some adverse effect on the growth properties of the host strain, their existence shows that two functioning chromosomal origins can coexist in one cell.Deletions generated from this type of plasmids allow an allocation of the origin of replication of E. coli within a DNA segment less than 0.4 MD in size.     

A two-year study of the distribution of ''thermophilic'' campylobacters in human, environmental and food samples from the Reading area with particular reference to toxin production and heat-stable serotype

The incidence of 'thermophilic' campylobacters in foods and environmental samples has been studied over a two-year period. Of 781 environmental samples, 529 (67%) were found to contain campylobacters, and campylobacters were isolated from 835 (39%) of 2116 food samples. Sewage was almost always contaminated with campylobacters (96·6% of samples) and of the food samples both poultry (55·5%) and offal (47·0%) were commonly contaminated. Determination of the heat-stable serotypes of all strains isolated from these sources and of 921 strains isolated from human faeces showed that there was a wide distribution of serotypes in most types of sample. Serotype Pen 2 was the commonest type found in human faeces (18·9%) and it was also commonest in offal (21·3%), beef (40·0%), sewage (17·7%) and was the third commonest type in poultry. A comparison of culture media and conditions for optimal production of both cytotoxic and cytotonic enterotoxins showed that Brucella Broth incubated under microaerobic conditions for 24 h at 42°C was suitable for both toxins. Detection of cytotoxic activity was most sensitive using HeLa cells. The sensitivities of two ELISA systems and a Chinese Hamster Ovary tissue culture assay for detection of cytotonic enterotoxin were comparable. Not all strains isolated from cases of enteritis in human beings produced toxin; 23·1% produced cytotonic enterotoxin and 17·5% produced cytotoxin. There was no correlation between serotype and toxin production. The wide distribution of campylobacters, indistinguishable from those isolated from cases of enteritis in human beings, leads us to conclude that simplistic statements suggesting that one particular type of food is primarily responsible for cases of human disease should not be made.     

An assessment of the Sartorius MD8 microbiological air sampler

Tests described in this paper show that gelatine membrane filters used in the MD8 microbiological air sampling system collected monodispersed aerosols between 0·7 and 1·0 μm containing viable Bacillus subtilis var. niger spores, with an efficiency of 99·9995%. Gelatine membrane filters linked to the MD8 control pump system were as effective as the well established Casella slit-to-agar device for collecting some viable bacteria, nebulized under controlled experimental conditions and naturally occurring airborne micro-organisms in a pharmaceutical plant. By using a long flexible hose connection to the control pump, the head could be positioned where sampling was required in locations remote from the pump exhaust, making it suitable for microbiological monitoring in critical locations such as laminar flow stations and isolators.     

High mortality of embryos of a distinct autochthonous Austrian coregonid population during Zuger jar incubation

For a distinct autochthonous Austrian coregonid population called Reinanke Coregonus sp., embryo viability was very low in Zuger jars (mean ± s.d. 36·1 ± 16·1% eyed stage embryos in experiment 1, 15·1 ± 17·0% in experiment 2) but high in vertical flow incubators (63·3 ± 29·0% eyed stage embryos in experiment 1, 57·8 ± 18·9% in experiment 2). Mechanical shock sensitivity is a possible explanation for high embryo mortality.     

The acute lethal toxicity of mixtures of cyanide and ammonia to smolts of salmon, Salmo salar L. at low concentrations of dissolved oxygen

The survival of Atlantic salmon smolts on exposure to constant concentrations of cyanide and ammonia, singly and together, has been measured under laboratory conditions at a concentration of 5 mgl^-1 of carbon dioxide. The 24-h LC50 values of cyanide and of un-ionised ammonia, in fresh water, were 0·073 mg HCN l^-1 and 0·20 mg NH₃l^-1 respectively at a concentration of dissolved oxygen of 10 mg l^-1, and 0·024 mg HCN l^-1 and 0·08 mgNH₃l^-1 respectively at a concentration of dissolved oxygen of 3·5 mg l^-1. In 30% sea water the corresponding values were similar for cyanide but markedly higher for ammonioa. In 80% sea water the values were intermediate between those of fresh water and 30% sea water. Prior acclimation of the fish to the respective toxicant increased the resistance of the fish only slightly to cyanide, but with ammonia the 24-h LC50 was increased between 1·4 and 2-fold after acclimation for 1–3 days to between 0·2 and 0·5 of the 24-h LC50 value. Mixtures of cyanide and ammonia were between 0·6 and 1·25 times as toxic as expected, assuming simple additivity of toxicity.