Bud and growth-unit structure in seedlings and saplings of Nothofagus alpina (Nothofagaceae)

In temperate trees, axis length growth generally results from the differentiation of organs at the end of a growing season and the extension of such "preformed organs" in the next growing season. Neoformation, i.e., the simultaneous differentiation and extension of organs, has been studied for only a few species. Here we evaluated bud composition and growth unit (GU) size for seedlings and saplings of Nothofagus alpina, a valuable South American forest tree. Trunk GUs of seedlings and saplings included preformed and neoformed organs, whereas main-branch GUs of saplings were entirely preformed. The size of a GU was more closely related to the number of preformed green leaves than to the number of cataphylls of its preceding bud. Proximal buds of a trunk GU had more cataphylls and less green-leaf primordia than distal buds. Individual leaf area increased from proximal to distal positions on trunk GUs. For trunk and main-branch GUs, the length/width ratio was maximum for leaves in intermediate positions. The development of large neoformed leaves at the end of the growing season could increase the photosynthetic capacity of this species in late summer, when the activity of preformed organs is likely to be decreasing.     

Improvement of the membrane filter technique for enumeration of enterococci in water

The membrane filter technique with AC agar medium supplemented with 0.04% NaN3 and 0.00015% 2,3,5-triphenyltetrazolium chloride for enumeration of enterococci in water is described. An appropriate volume of a water sample was filtered through the membrane filter. The membrane filter was put on an AC agar plate (designated as the AC.MF technique), which was incubated at 37 C for 18 hr and further at 45 C for 24 hr. By this AC.MF technique, all the colonies grown on the membrane filters were identified as enterococci, and the count of enterococci obtained by the AC.MF technique was similar to that by the AC.MPN technique. The AC.MF technique may be useful for accurate and rapid enumeration of enterococci in water and serve as a simple method for determining the sanitary quality of water.     

Statistical approach for comparison between methods of bacterial enumeration in drinking water

A general statistical procedure based on the likelihood ratio test is presented for the purpose of comparing estimates of mean bacterial density derived from different sets of data. This approach is much more appropriate than the conventional ways of analyzing bacteriological results (e.g., analysis of variance) which usually require previous transformation of the data. An illustrative application of the method compares three distinct titration techniques for enumerating heterotrophic bacteria in drinking water at 20°C incubation temperature. It was shown that both the standard plate count (SPC) and the membrane filter (MF) procedures supplied substantially the same information, whereas the microplate technique using the most probable number (MPN) for total bacterial enumeration could yield considerably different estimates: MPN values were significantly lower in three cases and significantly higher in one case out of a total of five experiments. The results consistently indicate a strong interaction between the technique used and the sample analyzed. Three different media (nutrient agar, R-2A low nutrient agar and m-SPC agar) were then evaluated for enumerating heterotrophic bacteria, using the MF technique at 48, 72 and 96 h of incubation time at 20°C. Although the media recovered approximately the same numbers of bacteria after 96 h of incubation, statistically significant discrepancies occurred after intermediate periods of incubation, perhaps because the relative rates of bacterial growth differed among media.     

Growth-unit structure in trees: effects of branch category and position on Nothofagus nervosa, N. obliqua and their hybrids (Nothofagaceae)

In plants with rhythmic growth, a branch segment extended in one event is known as growth unit (GU). GU structure, resulting from the resources allocated to stem length, volume and mass, and to leaf area and mass, is relevant for understanding branch functioning in the context of plant development. This study compares GU structure between main branches and short branches positioned at low and high positions on nursery-grown trees of three closely related genetic entities: Nothofagus nervosa, N. obliqua and natural hybrids between these species. GUs of short branches, compared to those of main branches, had lower length, diameter and number of leaves, and higher specific leaf area (SLA), stem density and proportional mass in leaves than in stems. GUs at high position on the trees had a higher proportion of their mass in stem than in leaves and a lower SLA than those at low position. Stem density was higher for N. nervosa and the hybrid trees than for N. obliqua. Most other GU traits did not differ statistically between the considered genetic entities. The three genetic entities exhibited distinct patterns of variation in leaf size with leaf position along main-branch GUs. The individual tree had a significant effect on most variables. GU structure would have a major ontogenetic component and would play a relevant role in the architecture of Nothofagus species and their adaptation to different environmental conditions.     

Comparison of the hydrophobic-grid membrane filter procedure and standard methods for coliform analysis of water

The hydrophobic-grid membrane filter (HGMF) has been proposed as an alternate method to the standard membrane filter (MF) procedure for the detection and enumeration of coliforms from water. Eight samples of nonchlorinated wastewater effluents were analyzed by the HGMF, standard MF, and tube fermentation most-probable-number methods for fecal coliforms, and eight samples each of polluted surface and dosed drinking waters were analyzed by the same methods for total coliforms. The drinking waters were dosed with coliforms and other heterotrophs concentrated from nonchlorinated domestic wastewater and treated with chlorine to reduce the numbers of organisms and simulate stress caused by chlorination. Statistical analyses determined that recoveries of fecal coliforms were significantly higher by the filtration methods for the nonchlorinated domestic wastewaters but not for the other waters. The results also indicated that recoveries of fecal and total coliforms did not differ significantly when either MFs or HGMFs were used. Total coliform results obtained with HGMFs having greater than 100 positive grid cells were significantly more precise than estimates obtained by the standard MF method only for polluted surface waters.     

Estimation of Escherichia coli in raw ground beef.

This study was undertaken to establish and evaluate more rapid methods of estimating Escherichia coli in ground beef than the standard most probable number (MPN) technique. Direct inoculation of and modifications to EC medium gave unreliable estimates of the presumptive E. coli count. Solid media incubated at an elevated temperature were compared to the MPN technique. Anderson and Baird-Parker's tryptone bile agar (TBA) method and prepoured plates of Endo, Levine eosin methylene blue (EMB), and violet red bile (VRBA) agars incubated at 44 degree C gave equivalent counts to the standard MPN method. Anderson and Baird-Parker TBA was the most selective solid medium for E. coli estimation, but all selective media incubated at elevated temperature reduced apparent E. coli counts by as much as 50%. Indole-producing and lactose-fermenting Enterobacteriaceae, capable of growth at elevated temperature, were tested for their growth on TBA, EMB, and VRBA at elevated temperature. TBA was selective for E. coli biotype I compared to other Enterobacteriaceae that predominate in meats. VRBA and EMB incubated at elevated temperature were not as selective as TBA, but differences in colonies could be observed between typical E. coli colonies and other Enterobacteriaceae on these media. Therefore, VRBA incubated at elevated temperature is proposed as a quality assurance screening test for presumptive E. coli in ground meat. Resuscitation techniques and prepoured plates with VRBA increased recovery levels of presumptive E. coli, but, under the conditions of this study, not to levels that represented a significant practical difference.     

Estimation of Escherichia coli in raw ground beef

This study was undertaken to establish and evaluate more rapid methods of estimating Escherichia coli in ground beef than the standard most probable number (MPN) technique. Direct inoculation of and modifications to EC medium gave unreliable estimates of the presumptive E. coli count. Solid media incubated at an elevated temperature were compared to the MPN technique. Anderson and Baird-Parker's tryptone bile agar (TBA) method and prepoured plates of Endo, Levine eosin methylene blue (EMB), and violet red bile (VRBA) agars incubated at 44 degree C gave equivalent counts to the standard MPN method. Anderson and Baird-Parker TBA was the most selective solid medium for E. coli estimation, but all selective media incubated at elevated temperature reduced apparent E. coli counts by as much as 50%. Indole-producing and lactose-fermenting Enterobacteriaceae, capable of growth at elevated temperature, were tested for their growth on TBA, EMB, and VRBA at elevated temperature. TBA was selective for E. coli biotype I compared to other Enterobacteriaceae that predominate in meats. VRBA and EMB incubated at elevated temperature were not as selective as TBA, but differences in colonies could be observed between typical E. coli colonies and other Enterobacteriaceae on these media. Therefore, VRBA incubated at elevated temperature is proposed as a quality assurance screening test for presumptive E. coli in ground meat. Resuscitation techniques and prepoured plates with VRBA increased recovery levels of presumptive E. coli, but, under the conditions of this study, not to levels that represented a significant practical difference.     

Comparison of the hydrophobic-grid membrane filter procedure and standard methods for coliform analysis of water.

The hydrophobic-grid membrane filter (HGMF) has been proposed as an alternate method to the standard membrane filter (MF) procedure for the detection and enumeration of coliforms from water. Eight samples of nonchlorinated wastewater effluents were analyzed by the HGMF, standard MF, and tube fermentation most-probable-number methods for fecal coliforms, and eight samples each of polluted surface and dosed drinking waters were analyzed by the same methods for total coliforms. The drinking waters were dosed with coliforms and other heterotrophs concentrated from nonchlorinated domestic wastewater and treated with chlorine to reduce the numbers of organisms and simulate stress caused by chlorination. Statistical analyses determined that recoveries of fecal coliforms were significantly higher by the filtration methods for the nonchlorinated domestic wastewaters but not for the other waters. The results also indicated that recoveries of fecal and total coliforms did not differ significantly when either MFs or HGMFs were used. Total coliform results obtained with HGMFs having greater than 100 positive grid cells were significantly more precise than estimates obtained by the standard MF method only for polluted surface waters.     

Similarities and gradients in growth unit branching patterns during ontogeny in "Fuji" apple trees: a stochastic approach

This study aims to explore and model the changes in growth unit (GU) branching patterns during tree ontogeny. The question was addressed in apple trees cv. "Fuji", by analysing the relative impact of GU length and within-tree position. The development of two 6-year-old trees was recorded over 6 years. The fate of axillary buds along each GU was represented as a sequence of symbols corresponding to five types of lateral growth: latent buds, short, medium, long, and floral lateral GUs. Based on an exploratory analysis of data and a priori hypotheses, a hidden semi-Markov chain was estimated from all of these GU sequences. This model was composed of six transient states representing successive branching zones along the GUs. The accuracy of this global model was a posteriori assessed by fitting the characteristic distributions computed from model parameters to the corresponding empirical characteristic distributions extracted from the observed sequences. The observed sequences were then grouped hierarchically according to the GU length, year of growth, and branching order. Comparing model parameters between these sub-groups revealed similarities between GUs. These similarities were based on particular branching zones whose composition and relative position within the GUs remained invariant across the subgroups: the latent zones, floral zone, and short-lateral zone. The probability of occurrence of the floral zone varied with the year, showing the alternate fruiting of "Fuji". It is shown that, during tree ontogeny, as GU length decreases, branching patterns tend to progressively simplify due to the disappearance of the most central zones and a progressive reduction in the length of the floral zone.     

Deciphering the ontogeny of a sympodial tree

This paper addresses the identification and characterization of developmental patterns in the whole structure of a sympodial species, the apple tree. Dedicated stochastic models (hidden variable-order Markov chains) were used to (i) categorise growth units (GUs) on the basis of their morphological characteristics (number of nodes and presence/absence of flowering) and position along axes, (ii) analyse dependencies between successive GUs and (iii) identify repeated patterns in GU sequences. Two successive phases, referred to as “adolescent” and “adult”, were identified in two apple tree cultivars. In the adolescent phase, “very” long monocyclic GUs were followed by long polycyclic GUs, whereas in the adult phase medium GUs were preferentially followed by short GUs. Flowering GUs constituted a preferential pathway between vegetative GUs of decreasing vigour (long, medium and short) and generated patterns that were interpreted with respect to fruiting regularity. The proposed modelling gave a global and quantitative picture of the two-scale structuring of apple tree ontogeny: a coarse scale corresponding to the succession of the previously mentioned phases and a fine scale corresponding to the alternation between flowering and vegetative GUs. This led us to propose a synthetic scheme of apple tree ontogeny that combines growth phases, polycyclism and flowering, and which could be transposed to other sympodial trees.     

疏水网格滤膜技术检测食源性致病菌的研究进展

疏水网格滤膜技术利用膜的疏水性黏附细菌细胞,通过膜的过滤作用截留细菌细胞,然后将膜进行选择性培养,达到检测鉴定待测菌的目的。主要概述了疏水网格滤膜技术的原理和特点,以及该技术与分子生物学技术、免疫学技术偶联在食源性致病菌检测中的应用。     

Rapid detection of Salmonella spp. in food by use of the ISO-GRID hydrophobic grid membrane filter.

A rapid hydrophobic grid-membrane filter (HGMF) method was developed and compared with the Health Protection Branch cultural method for the detection of Salmonella spp. in 798 spiked samples and 265 naturally contaminated samples of food. With the HGMF method, Salmonella spp. were isolated from 618 of the spiked samples and 190 of the naturally contaminated samples. The conventional method recovered Salmonella spp. from 622 spiked samples and 204 unspiked samples. The isolation rates from Salmonella-positive samples for the two methods were not significantly different (94.6% overall for the HGMF method and 96.7% for the conventional approach), but the HGMF results were available in only 2 to 3 days after sample receipt compared with 3 to 4 days by the conventional method.     

Conjugative Plasmid in Corynebacterium flaccumfaciens subsp. oortii That Confers Resistance to Arsenite, Arsenate, and Antimony(III)

The membrane filter (MF) method for detection and enumeration of coliform bacteria in drinking water requires that the coliforms both grow and produce a green metallic sheen when the filter is incubated on modified Endo medium at 35 degrees C for 22 h. Large numbers of noncoliform bacteria, which are enumerated by the standard plate count (SPC) technique, can interfere with the detection of coliforms on MF. This paper presents quantitative evidence from laboratory experiments on the interference of specific SPC bacteria on coliform colony sheen production on MF. Pseudomonas aeruginosa and Aeromonas hydrophila caused significant reductions in Escherichia coli sheen colony counts when present at 3,000 and 220 per filter, respectively. The Flavobacterium sp. and Bacillus sp. selected for this study from SPC did not interfere with coliform colony sheen production. Excessive crowding of E. coli and Enterobacter cloacae colonies on MF also caused a reduction in the number of colonies that produced sheen. Even when there was no crowding (14 colonies per filter), only a fraction of the E. cloacae colonies produced sheen colonies on modified Endo medium.     

Morphological and architectural features of young Nothofagus pumilio (Poepp. & Endl.) Krasser (Fagaceae)

The morphology and architecture of young Nothofagus pumilio plants growing as understorey and in a cleared area were assessed. Length, number of internodes, presence of branches and apex condition were registered for each growth unit (GU) in the sampled plant. GUs were grouped according to branching order and age of the bearing axis. Understorey plants were seven years old and had a short trunk bearing 2–3 orders of branches; all of their most recent GUs were horizontal and of comparable size. Plants growing in the cleared area were 10–16 years old and had a vigorous vertical and dominant trunk bearing 4–5 orders of less vigorous, horizontal branches. Plants from the cleared area showed signs of having had comparable-size GUs in all of their axes at a younger stage of growth. N. pumilio plants appear to start their growth with the production of short GUs in all of their axes irrespective of the light conditions. In contrast, the development of a vertical, vigorous trunk, seems to be restricted to plants growing in open environments.     

Rapid and automated enumeration of viable bacteria in compost using a micro-colony auto counting system

The micro-colony method was used to enumerate viable bacteria in composts. Cells were vacuum-filtered onto polycarbonate filters and incubated for 18 h on LB medium at 37 degrees C. Bacteria on the filters were stained with SYBR Green II, and enumerated using a newly developed micro-colony auto counting system which can automatically count micro-colonies on half the area of the filter within 90 s. A large number of bacteria in samples retained physiological activity and formed micro-colonies within 18 h, whereas most could not form large colonies on conventional media within 1 week. The results showed that this convenient technique can enumerate viable bacteria in compost rapidly for its efficient quality control.     

Gastric Ulcer Formation after the Hanshin-Awaji Earthquake: A Case Study of Helicobacter pylori Infection and Stress-Induced Gastric Ulcers

Background. Both Helicobacter pylori ( H. pylori ) infection and various stresses are known to induce peptic ulcer disease of the upper gastrointestinal tract. However, the pathogenetic relationship between the two factors has not yet been clarified. We conducted a case - control study to examine whether H. pylori infection played a role in the development of gastric ulcer (GU) induced by life-event stresses that were experienced after the Hanshin-Awaji earthquake.
Materials and Methods. Serum samples from patients in the devastated area who developed GUs during the 2 months following the Hanshin-Awaji earthquake and those from GU patients in the same area during the corresponding period of the previous year, and from gender-, age- and institute-matched ulcer-free controls were tested for the presence of the H. pylori IgG antibody.
Results. A significant association between H. pylori infection and the development of GU in uninjured patients was observed in all sets [matched odds ratio (OR) = 3.23, 95% confidence interval: 1.95–5.35]. Moreover, the prevalence of H. pylori infection in patients who developed GUs after the earthquake was not different from that for GU patients in the previous year. In contrast, there was no association between H. pylori infection and the development of GU in the physically injured patients after the earthquake.
Conclusions. H. pylori infection may play an important role in the development of GUs that are induced by emotional life-event stresses.     

Automation of microbial enumeration: development of a disposable hydrophobic grid-membrane filter unit

A disposable filter unit containing a hydrophobic grid-membrane filter (HGMF) was developed. The unit is liquid tight to serve as a specimen transport container and, by removal of the funnel extender (175- or 300-ml capacity), the unit becomes less than the height of two stacked petri plates to save space during in situ incubation. The polyethylene mesh which supports the HGMF facilitates rinse removal of any substance(s) that would interfere with microbial growth. The correlations between a pour plate, a conventional square HGMF, and a disposable filter unit on microbial enumeration were examined. Characteristics (e.g., clumping, spreading, etc.) of some microorganisms limit the linear counting range to less than 1,000 CFU per filter.     

Improved Aerobic Colony Count Technique for Hydrophobic Grid Membrane Filters

The AOAC International official action procedure for performing aerobic colony counts on hydrophobic grid membrane filters (HGMFs) uses Trypticase soy-fast green FCF agar (FGA) incubated for 48 h. Microbial growths are various shades of green on a pale green background, which can cause problems for automated as well as manual counting. HGMFs which had been incubated 24 or 48 h at 35°C on Trypticase soy agar were flooded underneath with 1 to 2 ml of 0.1% triphenyltetrazolium chloride (TTC) solution by simply lifting one corner of the filter while it was still on the agar and adding the reagent. Microbial growths on HGMFs were counted after color had been allowed to develop for 15 min at room temperature. With representative foods, virtually all colonies stained pink to red. Automated electronic counts made by using the MI-100 HGMF Interpreter were easier and more reliable than control HGMF counts made by the AOAC International official action procedure. Manual counting was easier as well because of increased visibility of the microbial growths. Except in the case of dairy products, 24-h TTC counts did not differ significantly from 48-h FGA counts, whereas the FGA counts at 24 h were always significantly lower, indicating that for many food products the HGMF TTC flooding method permits aerobic colony counts to be made after 24 h.     

Quantifying uncertainty associated with microbial count data: a Bayesian approach

We consider the problem of estimating bacterial concentration in a substance, given microbial count data. A Bayesian approach is proposed which naturally allows the incorporation of both plate-count data and extra information from confirmatory tests such as genotyping by polymerase chain reaction (PCR). The estimation methods yield posterior credible regions for bacterial concentration, in contrast to the previous methods, which generally only produce point estimates. The approach is illustrated with specific reference to the enumeration of the food-borne pathogen Escherichia coli O157 by spiral plating, although the methodology can be applied to any bacterium or counting method of interest. The results obtained provide guidance to the experimenter as to the number of confirmatory tests which should be performed, and also suggest that in the initial plate count one should err on the side of including rather than excluding colonies whose genotype seems unclear.     

Comparison and Assessment of Aerial and Ground Estimates of Waterbird Colonies

Abstract: Aerial surveys are often used to quantify sizes of waterbird colonies; however, these surveys would benefit from a better understanding of associated biases. We compared estimates of breeding pairs of waterbirds, in colonies across southern Louisiana, USA, made from the ground, fixed-wing aircraft, and a helicopter. We used a marked-subsample method for ground-counting colonies to obtain estimates of error and visibility bias. We made comparisons over 2 sampling periods: 1) surveys conducted on the same colonies using all 3 methods during 3–11 May 2005 and 2) an expanded fixed-wing and ground-survey comparison conducted over 4 periods (May and Jun, 2004–2005). Estimates from fixed-wing aircraft were approximately 65% higher than those from ground counts for overall estimated number of breeding pairs and for both dark and white-plumaged species. The coefficient of determination between estimates based on ground and fixed-wing aircraft was ≤0.40 for most species, and based on the assumption that estimates from the ground were closer to the true count, fixed-wing aerial surveys appeared to overestimate numbers of nesting birds of some species; this bias often increased with the size of the colony. Unlike estimates from fixed-wing aircraft, numbers of nesting pairs made from ground and helicopter surveys were very similar for all species we observed. Ground counts by one observer resulted in underestimated number of breeding pairs by 20% on average. The marked-subsample method provided an estimate of the number of missed nests as well as an estimate of precision. These estimates represent a major advantage of marked-subsample ground counts over aerial methods; however, ground counts are difficult in large or remote colonies. Helicopter surveys and ground counts provide less biased, more precise estimates of breeding pairs than do surveys made from fixed-wing aircraft. We recommend managers employ ground counts using double observers for surveying waterbird colonies when feasible. Fixed-wing aerial surveys may be suitable to determine colony activity and composition of common waterbird species. The most appropriate combination of survey approaches will be based on the need for precise and unbiased estimates, balanced with financial and logistical constraints. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):697–706; 2008)