Plants interact with microbial polysaccharides

Plants are resistant to almost all of the microorganisms with which they come in contact. In response to invasion by a fungus, bacterium, or a virus, many plants produce low molecular weight compounds, phytoalexins, which inhibit the growth of microorganisms. Phytoalexins are produced whether or not the invading microorganism is a pathogen. The production of phytoalexins appears to be a widespread mechanism by which plants attempt to defend themselves against pests. Molecules of microbial origin which trigger phytoalexin accumulation in plants are called elicitors. Structural polysaccharides from the mycelial walls of several fungi elicit phytoalexin accumlation in plants. Approximately 10 ng of the polysaccharide elicits the accumulation in plants of more than sufficient amounts of phytoalexin to stop the growth of microorganisms in vitro. The best characterized elicitors have been demonstrated to be β-1,3-glucans with branches to the 6 position of some of the glucosyl residues. Oligosaccharides, produced by partial acid hydrolysis of the mycelial wall glucans, are exceptionally active elicitors. The smallest oligosaccharide which is still an effective elicitor is composed of about 8 sugar residues. Bacteria also elicit phytoalexin accumulation in plants, but the Rhizobium symbionts of legumes presumably have a mechanism which allows them to avoid either eliciting phytoalexin accumulation or the effects of the phytoalexins if they are accumulated. The lectins of legumes bind to the lipopolysaccharides of their symbiont, but not of their non-symbiont, Rhizobium. It is not known whether the lectin-lipopolysaccharide interaction is involved with the establishment of symbiosis. However, evidence will be presented that suggests that lectins are, in fact, enzymes capable of modifying the structurs of the lipopolysaccharides of their symbiont, but not of their non-symbiont, Rhizobium. It will also be shown that the lipopolysaccharides isolated from different Rhizobium species and from different strains of individual Rhizobium species have different sugar compositions. Thus, the different strains of a single Rhizobium species are as different from one another as the different species of Salmonella and other gram-negative bacteria. This conclusion is substantiated by experiments demonstrating that antibodies to the lipopolysaccharide from a single Rhizobium strain can differentiate that strain from other strains of the same species as well as from other Rhizobium species. The role in symbiosis of the strain-specific O-antigens is unknown.     

BRAIN pH MEASUREMENTS USING A DIFFUSIBLE, LIPID SOLUBLE pH SENSITIVE FLUORESCENT INDICATOR

Brain tissue pH was measured in cats at normocapnia hypocapnia, hypercapnia, and death from anoxia using a pH sensitive fluorescent indicator (umbelliferone) with both molecular and ionic fluorophors. A ratio analysis of the indicator's calibrated 450 nm fluorescent tissue washout curves from 340 and 370 nm excitation permitted direct determinations using a nomogram. Possible errors in these measurements related to differential quenching, absorption, and changes in the redox state of the indicator were investigated in vitro and in vivo for brain tissue and blood. In animals with preserved autoregulation, brain pH varied linearly with arterial pH (art pH 7.0, brain pH 6.98: art pH 7.4, brain pH 7.24). Brain pH at death fell to 6.68. An analysis of the indicator clearance curves suggests these measurements reflect a component of the intracellular space and the lipid solubility of the indicator suggests this is a membranous component.     

SCANNING ELECTRON MICROSCOPE OBSERVATINS ON ZOOSPORANGIAL ABSCISSION IN PHYCOPELTIS EPIPHYTON (CHLOROPHYA)1

Zoosporangial abscissin in asexually reproductive Phycopeltis epiphyon, Millardet, epiphytic on leaces of Osmanhus fragrans Loureiro and Sabal minor (Jacquin) Person, examined with scanning electron micrsscopy is described and compared with the process in related Cephaleuros virescens Kunze. The laeral wall of he zoosporangium-pedicel septum begins to rupure early in he abscission process and is followed by continued learing of the lateral wall and partial spliing of the septum. The zoosporangium remains attached in a hinge-like fashion to the pedicel by a portion of the lateral wall and septum. A centrally located protuberance emerges from wihin the septa of both the zoosporangium and pedicel, and together with a slight bulging of the septa, is involved in the final separation of the zoosporangium. Although there are differences in surface morphlogy of identical in P. the zoosporangia and the location of the exit pores, the process of abscission is identical in P. epiphyton and C. virescens.     

A fermentation process for producing both ethanol and lysine-enriched yeast.

In 18 batch-fermentation experiments, baker's yeast was grown in an enriched mineral medium, containing 10% by weight glucose, at various pH and temperature levels. The pH and temperature are just two representative engineering variables which can be easily varied at negligible cost. The commercial yeast inoculum, 20% by weight or about .16% viable cells, was selected to represent industrial (nonsterile) conditions. Free L-lysine, ethanol, and cell growth were followed in time for each batch run held at a fixed pH and temperature. The maximum free lysine level reached at either 10 1/2 or 24 hr occurred at a pH of 5 and 32 degrees C. At 24 hr, the peak free lysine level, 120 mg/liter, is three times as great as the uncontrolled pH counterpart. In terms of total L-lysine (free plus protein-bound) the peak represents a 25% improvement over the uncontrolled case, based on an average 3.5% lysine level per cell weight. The greatest measured cell level, .9% by weight in the fermentation broth, or a 5 1/2-fold increase over th inoculum, was reached during the 36 degrees C and pH 3 run, while the largest measured ethanol value (3%, or 30% conversion by weight from glucose) was achieved during the 28 degrees C and pH 6 experiment. The optimal lysine run product, however, no less than 15% of the maximum cell and 30% of the maximum ethanol levels.     

Amaurosis fugax and carotid artery disease: indications for angiography.

A prospective study of 80 patients presenting with amaurosis fugax was performed in an attempt to relate clinical features to angiographic findings in the internal carotid artery. Carotid bruit, transient cerebral ischaemic attacks, hypertension, and claudication were associated with a high prevalence of angiographic abnormality. Every patient who showed all these features had an operable lesion, as did 88% of those who had three features. In patients over 50 years of age carotid stenosis and atheromatous ulceration were occasionally found in the absence of bruit and transient cerebral ischaemia, but only one patient aged under 50 had an operable lesion and no associated features. Clinical features were therefore valuable in predicting the outcome of angiography, but it seems prudent to restrict angiography to patients aged over 50, who are most likely to benefit from surgery on the carotid artery.     

Fatty acid positional distribution in phospholipids of a psychrophilic bacterium during changes in growth temperature

The major phospholipids of the psychrophilic bacteriumMicrococcus cryophilus, phosphatidylethanolamine and phosphatidylglycerol, have similar fatty acid compositions, comprising almost entirely palmitoleic and oleic acids. We show that there is a preference for the longer chains in thesn-1 position of both phosphatidylethanolamine and phosphatidylglycerol, both during isothermal growth and after temperature shifts, despite the fact that the overall phospholipid C18/C16 acyl chain ratio decreases with a lowering of growth temperature. Although it has been shown using model systems that the isomeric configurationsn-1-long,sn-2-short lowers lipid melting temperature, this paper reports the first clear-cut demonstration of such an isomeric preference in a natural system. We discuss how this acyl chain configuration contributes to membrane fluidity inM. cryophilus, in terms of adaptation to its psychrophilic habitat.     

Protein extraction and activity in reverse micelles of a nonionic detergent

We describe, for the first time, the ability of a polyoxyethylene sorbitan trioleate-isopropanol microemulsion in hexane to solubilize pure proteins. The dependences of cytochrome c extraction and buffer solubilization by the reverse micellar system on ionic strength of the aqueous phase, detergent concentration, and cosurfactant concentration result in increased extraction. In addition, subtilisin (a serine protease) is shown to be active in this microemulsion. Further the activity of the enzyme can be regulated by the water content of the micelles, enabling control of enzyme activity by "solvent engineering."     

Effect of hydration on the morphology of enzyme powder

We report the first direct images of the hydration of protein powders. Using an environmental scanning electron microscope (ESEM) we have taken a series of micrographs of a region of the enzyme (subtilisin) power whilst hydrating the sample. In addition, the sample has been viewed during exposure to toluene vapors. The ESEM is a remarkable new instrument that will have wide applicability in imaging of biological materials in their native environments.