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101.
C W Forsberg L K Lovelock L Krumholz J G Buchanan-Smith 《Applied and environmental microbiology》1984,47(1):101-110
Intact, metabolically active rumen protozoa prepared by gravity sedimentation and washing in a mineral solution at 10 to 15 degrees C had comparatively low proteolytic activity on azocasein and low endogenous proteolytic activity. Protozoa washed in 0.1 M potassium phosphate buffer (pH 6.8) at 4 degrees C and stored on ice autolysed when they were warmed to 39 degrees C. They also exhibited low proteolytic activity on azocasein, but they had a high endogenous proteolytic activity with a pH optimum of 5.8. The endogenous proteolytic activity was inhibited by cysteine proteinase inhibitors, for example, iodoacetate (63.1%) and the aspartic proteinase inhibitor, pepstatin (43.9%). Inhibitors specific for serine proteinases and metalloproteinases were without effect. The serine and cysteine proteinase inhibitors of microbial origin, including antipain, chymostatin, and leupeptin, caused up to 67% inhibition of endogenous proteolysis. Hydrolysis of casein by protozoa autolysates was also inhibited by cysteine proteinase inhibitors. Some of the inhibitors decreased endogenous deamination, in particular, phosphoramidon, which had little inhibitory effect on proteolysis. Protozoal and bacterial preparations exhibited low hydrolytic activities on synthetic proteinase and carboxypeptidase substrates, although the protozoa had 10 to 78 times greater hydrolytic activity (per milligram of protein) than bacteria on the synthetic aminopeptidase substrates L-leucine-p-nitroanilide, L-leucine-beta-naphthylamide, and L-leucinamide. The aminopeptidase activity was partially inhibited by bestatin. It was concluded that cysteine proteinases and, to a lesser extent, aspartic proteinases are primarily responsible for proteolysis in autolysates of rumen protozoa. The protozoal autolysates had high aminopeptidase activity; low deaminase activity was observed on endogenous amino acids. 相似文献
102.
Summary Techniques are described in this paper for growing Nitrosomonas europea in batch and in continuous culture with apparatus constructed from readily available laboratory materials.The methods employed in batch culture have enabled the collection of cells concentrated in small volumes.
Nitrosomonas europaea has been grown successfully in continuous culture and yields of 23 g wet weight were obtained, an average of 0.16 g/l with a flow rate of 300 ml/h over twenty days. Results show that high levels of nitrite do not materially affect the growth of the bacterium. The continuous culture equipment has also been used to grow Azotobacter vinelandii and Thiobacillus concretivorus. 相似文献
103.
104.
J. M. Cheeseman B. F. Clough D. R. Carter C. E. Lovelock Ong Jin Eong R. G. Sim 《Photosynthesis research》1991,29(1):11-22
In this report, we analyze the photosynthetic capacity and performance of leaves under field conditions with a case study based on the mangroves Bruguiera parviflora and B. gymnorrhiza. Using a tower through a closed canopy at a field sight in North Queensland and portable infra-red gas analyzers, a large data set was collected over a period of 11 days early in the growing season. The set was used to analyze the relationship between net photosynthesis (Pnet) and light, leaf temperature, stomatal conductance and intracellular CO2 (Ci).There are three objectives of this report: (1) to determine photosynthetic potential as indicated by the in situ responses of Pnet to light and stomatal conductance, (2) to determine the extent to which photosynthetic performance may be reduced from that potential, and (3) to explore the basis for and physiological significance of the reduction.The results indicate that even under harsh tropical conditions, the mangrove photosynthetic machinery is capable of operating efficiently at low light and with maximal rates of more than 15 mol CO2 m-2 s-1. Though stomata were more often limiting than light, in any single measurement the average reduction of Pnet from the maximum value predicted by light or conductance responses was 35%. Analysis of single leaf light and CO2 responses indicated that photosynthetic performance was under direct photosynthetic, or non-stomatal, control at all light and conductance levels. Capacity was adjustable rapidly from a maximum value to essentially nil such that Ci varied inversely with Pnet from ca. 150 L L-1 at the highest rates of CO2 exchange to ambient at the lowest. 相似文献
105.
Bayesian adaptive sequence alignment algorithms 总被引:3,自引:1,他引:2
The selection of a scoring matrix and gap penalty parameters continues to
be an important problem in sequence alignment. We describe here an
algorithm, the 'Bayes block aligner, which bypasses this requirement.
Instead of requiring a fixed set of parameter settings, this algorithm
returns the Bayesian posterior probability for the number of gaps and for
the scoring matrices in any series of interest. Furthermore, instead of
returning the single best alignment for the chosen parameter settings, this
algorithm returns the posterior distribution of all alignments considering
the full range of gapping and scoring matrices selected, weighing each in
proportion to its probability based on the data. We compared the Bayes
aligner with the popular Smith-Waterman algorithm with parameter settings
from the literature which had been optimized for the identification of
structural neighbors, and found that the Bayes aligner correctly identified
more structural neighbors. In a detailed examination of the alignment of a
pair of kinase and a pair of GTPase sequences, we illustrate the
algorithm's potential to identify subsequences that are conserved to
different degrees. In addition, this example shows that the Bayes aligner
returns an alignment-free assessment of the distance between a pair of
sequences.
相似文献
106.
After defoliation by herbivores, some plants exhibit enhanced rates of photosynthesis and growth that enable them to compensate for lost tissue, thus maintaining their fitness relative to competing, undefoliated plants. Our aim was to determine whether compensatory photosynthesis and growth would be altered by increasing concentrations of atmospheric CO2. Defoliation of developing leaflets on seedlings of a tropical tree, Copaifera aromatica, caused increases in photosynthesis under ambient CO2, but not under elevated CO2. An enhancement in the development of buds in the leaf axils followed defoliation at ambient levels of CO2. In contrast, under elevated CO2, enhanced development of buds occurred in undefoliated plants with no further enhancement in bud development due to exposure to elevated CO2. Growth of leaf area after defoliation was increased, particularly under elevated CO2. Despite this increase, defoliated plants grown under elevated CO2 were further from compensating for tissue lost during defoliation after 51/2 weeks than those grown under ambient CO2 concentrations. 相似文献
107.
Feller Ilka C. Berger Uta Chapman Samantha K. Dangremond Emily M. Dix Nicole G. Langley J. Adam Lovelock Catherine E. Osborne Todd Z. Shor Audrey C. Simpson Loraé T. 《Ecosystems》2023,26(4):800-814
Ecosystems - Low temperature stress is the primary factor determining the latitudinal limits of tropical plants. As the climate warms, tropical species are migrating poleward, displacing native... 相似文献
108.
Nataly Gutierrez-Isaza Eugenia M. Sampayo Catherine E. Lovelock Steven J. Dalton Carrie A. Sims Selina Ward John M. Pandolfi 《Global Ecology and Biogeography》2023,32(3):421-434
Aim
The aims were to test the role of temperature in latitudinal patterns of egg size and investigate maternal investment trade-offs among coral taxa.Location
Global, from 34° S to 34° N.Time period
1981–2020.Major taxa studied
Reef coral species from the order Scleractinia.Methods
We compiled a comprehensive geo-referenced global dataset of egg sizes (diameter or volume) and fecundity (number of eggs per area) for colonial corals (Scleractinia; 123 species, 5359 observations and 39 localities), substantially enhanced by new field collections (>88% of observations). We used Bayesian phylogenetic multilevel models to test for Rass' rule (a hypothesized negative relationship between egg size and temperature); we also included other environmental variables and life history traits. We also tested whether a trade-off exists between egg size and fecundity in broadcast spawning hermaphroditic corals with horizontal symbiont transmission (HHT).Results
We found a significant relationship between coral egg size and symbiont transmission. Eggs from coral species with vertical symbiont transmission were c. 18.8% smaller than those from species with horizontal symbiont transmission. We also found non-significant relationships between egg size and sea surface temperature (SST) for broadcast spawning corals and between egg size and fecundity specifically for HHT species.Main conclusions
Contrary to recognized latitudinal patterns of egg size across taxa, our study does not provide support for Rass' rule in corals. Additionally, our findings do not support a maternal investment trade-off between egg size and fecundity for HHT species. Our study used a phylogenetic framework that should be a standard practice when studying interspecific variation, including investigation of maternal investment and identification of the influence of multiple predictors on larval fitness (egg size), in addition to trade-offs affecting propagule influx (fecundity). Both these functional traits are vital and have direct consequences for population maintenance and connectivity in sessile organisms, such as corals. 相似文献109.
110.