Fate of mucilage cell wall polysaccharides during coffee fermentation.

Effects of a 20-h fermentation on cell wall polysaccharides from the mucilage of pulped coffee beans were examined and compared to those of unfermented beans, on alcohol insoluble residues (AIRs), their hot-water-soluble crude pectic substances (PECTs), and their hot-water-insoluble residues (RESs). Yields and compositions were very similar: AIRs, which consisted of approximately 30% highly methylated pectic substances, approximately 9% cellulose, and approximately 15% neutral noncellulosic polysaccharides, exhibited no apparent degradation. However, PECTs from fermented beans were shown to have undergone a slight reduction of their intrinsic viscosity and weight-average molecular weight by capillary viscosimetry and high-performance size-exclusion chromatography. After fermentation, hot-water-insoluble pectic substances of RES exhibited partial de-esterification. Removal of coffee bean mucilage by natural fermentation seems to result from a restricted pectolysis, the mechanism of which remains to be elucidated.     

Survival of myxobacter strain 8 in natural soil in the presence and absence of host cells

Myxobacter strain 8 is one component of a sequence of three predatory bacteria that develop in soil when Micrococcus luteus host cells are added to the soil. The survival of strain 8 in the presence and absence of added host cells in natural soil not allowed to dry out was examined. Strain 8 vegetative cells died relatively rapidly in unamended soil. Death was faster and occurred to a greater extent in acidic than in neutral pH soil. However, in both cases death was accompanied by formation of sonication-resistant myxospores so that they comprised the ultimate population. These myxospores survived for prolonged periods in both acidic and neutral pH soils.Vegetative cells added in high numbers to soil did not multiply under any of the conditions tested. They did multiply, however, when they were added in low numbers to soil (including acidic soil) receiving sequential (additive) amendments of heart infusion broth or living M. luteus cells. This multiplication produced strain 8 cell numbers approximating those in the above experiments receiving high strain 8 cell number inoculations. Possibly, this represents a maximum vegetative cell number for soil.Germination of the myxospores in soil, followed by growth, seemed to require an approximately neutral pH and the presence of a proper host organism. Germination occurred with M. luteus as host, but not with Escherichia coli. A delayed germination occurred when sequential amendments of heart infusion broth, instead of M. luteus host cells, were made, but this could reflect a growth response by some indigenous components of the soil microflora that then served as host cells for germination.     

Otto Appel

Ohne Zusammenfassung

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Otto Appel

     

Biotypes of the citrus nematode (Tylenchulus semipenetrans Cobb) in Israel

Two biotypes of the citrus nematode, Tylenchulus semipenetrans Cobb, were identified among five populations occurring in different regions in Israel. These biotypes originated from Sour orange and Troyer citrange roots and differed in their ability to infestPoncirus trifoliata hybrids (particularly Troyer citrange). They appear to be close to two recognized biotypes known to be present in other countries and designated as the “Poncirus” and “Mediterranean” biotypes. The different infectivity of the two biotypes on Troyer citrange roots was maintained even after they were cultured for 6 months on Sour orange. Both biotypes readily reproduced on persimmon, but failed to infest olive and grapevine. Two newP. trifoliata x Poorman orange hybrids exhibited good resistance to both biotypes.     

Laboratory selection of resistance by the red flour beetle,tribolium castaneum (Herbst), to an atmosphere of low oxygen concentration

Adult populations of the red flour beetle,Tribolium castaneum (Herbst), were exposed for 40 generations to an atmosphere containing 99.5% N₂ and 0.5% O₂ at 95% RH, in order to select a strain resistant to the low oxygen concentration (LOC) atmosphere. Selection pressure was maintained at between 50% and 70% mortality. At the 40th generation comparison of sensitivity between the selected strain and the original non-selected strain indicated a resistance factor at the 50% mortality level (LT50) of x 5.2. However, throughout the selections, log-time against probit-mortality curves remained roughly parallel from generation to generation and the slope remained low. These findings indicate a multiplicity of genetic factors that at a high level of selection contribute together towards an adaptation of the insects to survival in the LOC atmosphere. Removal of selection pressure from a sub-population of the selected strain from the 13th to 21st generation revealed that resistance was partially retained with a decrease in resistance factor of 23%. Although the study revealed that the insects were able to develop a strain resistant to hypoxia, exposures were at 95% RH to minimize the desiccation effect. This does not reflect field situations, where ambient relative humidities are generally below 70%.     

Simultaneous one-tube quantification of host and pathogen DNA with real-time polymerase chain reaction

ABSTRACT Phaeocryptopus gaeumannii is a widespread foliar parasite of Douglas-fir. Although normally innocuous, the fungus also causes the defoliating disease Swiss needle cast in heavily infected needles. The extent of P. gaeumannii colonization in Douglas-fir foliage was estimated with real-time quantitative polymerase chain reaction (PCR) using TaqMan chemistry. In order to derive a normalized expression of colonization, both pathogen and host DNA were simultaneously amplified but individually detected by species-specific primers and TaqMan probes labeled with different fluorescent dyes. Detection of host DNA additionally provided an endogenous reference that served as both an internal positive control and adjusted for variation introduced by sample-to-sample differences in DNA extraction and PCR efficiencies. The genes employed for designing the TaqMan probes and primers were beta-tubulin for the pathogen and a LEAFY/FLORICAULA-like gene involved in floral development for the tree host. Both probe/primer sets exhibited high precision and reproducibility over a linear range of 4 orders of magnitude. This eliminated the need to analyze samples in multiple dilutions when comparing lightly with heavily infected needles. Quantification of the fungus within needles was successful as early as 1 month after initial infection. Real-time PCR is the only method currently available to quantify P. gaeumannii colonization early in the first year of the colonization process.     

Plant-parasitic nematodes of Croatia1

Investigations on the distribution of nematodes were carried out mostly in the northern and eastern parts of Croatia up to 1991. Sampling was performed in the following crops: maize, wheat, barley, sugarbeet, soybean, sunflower, rape, tobacco, potato, alfalfa, blackberry, onion, carrot, cucumber, lettuce, tomato, capsicum, oak, chrysanthemum, tulip, rose, grapevine, peach, apple, plum, pear, cherry, poplar, willow, clover, nettle, grass, meadow, woodland, many species of weeds, various glasshouse crops and vegetation in a nature reserve. 63 genera of nematodes with 81 species were detected. The most numerous representatives of plant parasitic nematodes were: Anguina, Aphelenchoides, Aphelenchus, Criconemoides, Ditylenchus, Gracilacus, Helicotylenchus, Hemicycliophora, Heterodera, Longidorus, Macroposthonia, Meloidogyne, Paratylenchus, Pratylenchus, Rotylenchulus, Rotylenchus, Trichodorus, Tylenchorhynchus, Tylenchus and Xiphinema.