Response in Soil of Cupriavidus necator and Other Copper-Resistant Bacterial Predators of Bacteria to Addition of Water, Soluble Nutrients, Various Bacterial Species, or Bacillus thuringiensis Spores and Crystals

Soil was incubated with various species of bacteria, Bacillus subtilis, or Bacillus thuringiensis spores and crystals. These were added to serve as potential prey for indigenous, copper-resistant, nonobligate bacterial predators of bacteria in the soil. Alternatively, the soil was incubated with soluble nutrients or water only to cause potential indigenous prey cells to multiply so the predator cells would multiply. All of these incubation procedures caused excessive multiplication of some gram-negative bacteria in soil. Even greater multiplication, however, often occurred for certain copper-resistant bacterial predators of bacteria that made up a part of the gram-negative response. Incubation of the soil with copper per se did not give these responses. In most cases, the copper-resistant bacteria that responded were Cupriavidus necator, bacterial predator L-2, or previously unknown bacteria that resembled them. As was the case for C. necator and L-2, these new bacteria did not use glucose, had white colonies, produced copper-related growth initiation factor (GIF), and attacked B. thuringiensis spores on laboratory media. The results were different, however, when B. thuringiensis spores and crystals per se were added to the soil. The copper-resistant bacterial response in the soil did not, to any extent, include C. necator-like bacteria. Instead, the main copper-resistant bacterial predators that developed had yellow colonies and did not resemble C. necator or L-2 in other ways. They were not seen before, and they did not develop on the addition of B. subtilis spores to soil. Apparently, they could not produce a C. necator-like GIF. Nevertheless, they did respond very quickly to B. thuringiensis spores and crystals in soil, as if a GIF of some sort were involved. These results suggest that, under various conditions of soil incubation, gram-negative bacterial predators of bacteria multiply and that several copper-resistant types among them can be detected, counted, and isolated by plating dilutions of the soil onto media containing excess copper.     

Interaction of Agromyces ramosus with Other Bacteria in Soil

Agromyces ramosus occurs in very high numbers in most soils and, based on studies of laboratory isolates, does not require host cells for growth. Nevertheless, it attacked and destroyed most of the gram-positive and gram-negative bacterial species tested as possible host organisms. A. ramosus also attacked and destroyed Saccharomyces cerevisiae. The possibility of attack on fungi was unclear. Among the bacteria serving as hosts were the important soil species Azotobacter vinelandii, Rhizobium leguminosarum, Rhizobium meliloti, and Agrobacterium tumefaciens. Dead cells were not attacked. A. vinelandii cysts were attacked but left unharmed. To some extent, A. vinelandii seemed to survive this attack by encysting. Attack by A. ramosus occurred in natural soil and over a broad range of nutritional levels in laboratory media. The attack did not seem to be a means for obtaining an increased supply of commonly available nutrients. Instead, it seemed to be a means of obtaining something produced, perhaps in small amounts, by a variety of organisms, but not by all organisms. Several types of culture filtrates were tested for activity. The filtrates neither stimulated nor inhibited the growth of A. ramosus or the host organisms. The availability of catalase activity in host organisms did not seem to be involved. It is not known whether the attack by Agromyces ramosus in soil can be manipulated to cause a decrease in numbers of Agrobacterium tumefaciens or other pathogens without simultaneously depressing the numbers of beneficial organisms in this habitat.     

Effect of Protozoa on Bacterial Degradation of an Aromatic Compound

Prototrophic and growth factor-requiring strains of Alcaligenes spp. were used to study the effect of a protozoan, Tetrahymena pyriformis, on the degradation of p-aminobenzoate. The protozoan inhibited activity of the prototrophic bacterium by reducing its population size. For the growth factor-requiring strain of Alcaligenes, T. pyriformis provided the required growth factors so that the predator permitted the bacteria to grow and to continue p-aminobenzoate degradation. T. pyriformis inhibited bacterial activity when the amino acid supply was in excess, but activity of the auxotrophic strain of Alcaligenes was stimulated by the protozoan when the amino acid supply was limiting, although the bacterial population size was reduced by the protozoan.     

Copper sulfide precipitation by yeasts from Acid mine-waters

Two strains of Rhodotorula and one of Trichosporon precipitated dissolved copper with H₂S formed by reducing elemental sulfur with glucose. Iron stimulated this activity under certain conditions. In the case of Rhodotorula strain L, iron stimulated copper precipitation aerobically at a copper concentration of 18 but not 180 μg/ml. Anaerobically, the L strain required iron for precipitation of copper from a medium with 180 μg of copper per ml. Rhodotorula strain L was able to precipitate about five times as much copper anaerobically as aerobically. The precipitated copper was identified as copper sulfide, but its exact composition could not be ascertained. Iron was not precipitated by the H₂S formed by any of the yeasts. Added as ferric iron, it was able to redissolve copper sulfide formed aerobically by Rhodotorula strain L from 18 but not 180 μg of copper per ml of medium. Since the yeasts were derived from acid mine-waters, their ability to precipitate copper may be of geomicrobial importance.     

A Growth Initiation Factor for Host-Independent Derivatives of Bdellovibrio bacteriovorus

Host-independent (H-I) derivatives of Bdellovibrio bacteriovorus 109 Davis could not be isolated when concentrated suspensions of host-dependent (H-D) cultures, washed free of spent medium, were plated on host-free media. However, H-I colonies did appear when spent broth was incorporated into the isolation medium, indicating the presence of a factor in the spent medium essential for the growth of H-I cells. This growth factor (GIF) was also present in cell-free extracts of Escherichia coli and a variety of other microorganisms including H-D and H-I derivatives of strain 109 Davis. GIF was heat stable, non-dialyzable, and present in both soluble and particulate fractions of extracts. Heating of extracts at 70 C for 10 min resulted in 10- to 40-fold stimulation in GIF activity, and evidence for a heat-labile inhibitor was obtained. Colonies appearing on host-free medium in these experiments were shown to be those of typical H-I derivatives by isolation and subsequent host-independent cultivation of these organisms. GIF was a conditional requirement dependent on age and size of inoculum for all H-I derivatives characterized. Although GIF stimulated the growth of washed exponential phase cells transferred to fresh medium, it was not essential for growth. However, it was essential for the initiation of growth of washed stationary phase cells from small inocula transferred to fresh medium. It is proposed that GIF is required to initiate growth of metabolically quiescent cells.     

Effects of amino acids on polysaccharide synthesis ofEscherichia coli K-12lon + andlon − strains

Ultraviolet-sensitivelon ^? mutant ofEscherichia coli K-12 produced abundant polysaccharide when grown in a minimal medium at 37 C, but not when grown in a broth medium. The repression of polysaccharide synthesis in the broth-grownlon ^? andlon ⁺ cells was studied. The effects were largely dependent on the amino acid concentrations and on the requirements of the strain used. At 200 μg per ml of each of the essential amino acids, histidine, proline, and threonine, there was complete inhibition of polysaccharide synthesis. At 200 μg per ml the required amino acids, tryptophane and tyrosine promoted polysaccharide synthesis. Most amino acids inhibited cell growth at 200 μg per ml but the inhibiting effect was smaller at 400 μg per ml. Polysaccharide synthesis of cells was not correlated with the growth rate, and occurred even under non-growing conditions.     

Initiation and Velocity of Chromosome Replication in Escherichia coli B/r and K-12

The macromolecular composition and a number of parameters affecting chromosome replication were examined over a range of exponential growth rates in two common Escherichia coli strains, B/r and K-12 AB1157. Based on improved measurements of DNA after treatment of exponential cultures with rifampin, the cell mass per chromosomal replication origin (initiation mass) and the time required to replicate the chromosome from origin to terminus (C period) were determined. For these two strains, the initiation mass approached values of 8 × 10⁻¹⁰ and 10 × 10⁻¹⁰ units of optical density (at 460 nm) of culture mass per oriC, respectively, at growth rates above 1 doubling/h (at 37°C). The amount of protein per oriC decreased with increasing growth rate for AB1157 and remained nearly constant for the B/r strain. The C period decreased for both strains in an essentially identical manner from about 70 min at 0.6 doublings/h to about 33 min at 3 doublings/h. From the initiation mass and C period, relative or absolute copy numbers for genes with known map locations can be accurately determined at different growth rates. At growth rates above 2 doublings/h, when chromosomes are highly branched, genes near the origin are about threefold more prevalent than genes near the terminus. At a growth rate of 0.6 doubling/h, this ratio is only about 1.7, which reflects the lower degree of chromosome branching.     

Enhanced production of peroxidase in continuous culture of Arthromyces ramosus by selective bleeding of mycelium

A new method of continuous culture with selective bleeding of mycelia using 9-mesh screen was developed to improve the production rate of peroxidase (POD) by Arthromyces ramosus. At the dilution rate of 0.05 h⁻¹ with the mycelium leakage rate of 60%, a high production rate (average value was 1.67 U·ml⁻¹·h⁻¹) was maintained for over 100 h: the rate was 3.2 times that in a glucose-fed batch culture. At the same dilution rate, the volumetric and specific production rates of POD in the continuous culture without the screen were lower than those in the first continuous culture and decreased gradually in the later phase of the culture. In the continuous culture with low mycelium leakage rate of 1.6%, the POD production rate was not improved further, although the mycelial concentration (43 g·l⁻¹) increased 2.9 times. It is suggested that the high agitation rate required to meet the oxygen demand is unfavorable for the POD production.     

Medetera aldrichii larval feeding behavior and prey consumption [Dipt.: Dolichopodidae]

Predatory behavior ofMedetera aldrichii Wheeler (Dolichopodidae) larvae was observed in bark-Lucite sandwiches infested with immature broods of the bark beetle preyDendroctonus pseudotsugae Hopkins (Scolytidae). Predator larvae could not penetrate unmined phloem or prey galleries tightly packed with frass, but moved through loose frass and bark-Lucite interspaces formed when the mined inner bark dried. At high prey densities interspace formation and gallerly contiguity enabled the predator to move freely and attack several prey in rapid succession. At low prey densities the predator was frequently isolated from prey by impenetrable strips of phloem. Predator larvae maintained singly in small plastic arenas consumed an average of 14.7 immature prey, but required only 6.2 prey when reared exclusively on large prey.     

Prototheca zopfii Krüger Strain UMK-13 Growth on Acetate or n-Alkanes

A new strain of Prototheca zopfii Krüger was grown on acetate or on pure n-alkanes. A maximum acetate-supported exponential growth of 12 divisions day⁻¹ occurred at pH 5 and 30°C. At 25°C, growth on n-alkanes was almost as fast, but no growth occurred at 30°C. After 4 days at 25°C, 34 to 45% of the n-alkanes had been removed, whereas at 21°C and slower growth, utilization was twofold greater after 15 days. Rates of growth and utilization increased markedly after a point of sudden emulsification.     

Soybean Nodule-Specific Uricase (Nodulin-35) Is Expressed and Assembled into a Functional Tetrameric Holoenzyme in Escherichia coli

A complete nodulin-35 (N-35) cDNA encoding nodule-specific uricase (EC 1.7.3.3) was isolated from a soybean (Glycine max L. var. Prize) nodule cDNA expression library using a previously isolated partial cDNA clone. The N-35 cDNA was expressed in Escherichia coli driven by the lacZ promoter and was found to be functionally active. The uricase activity was detected in the cytoplasmic fraction of E. coli with the same pH optimum and apparent K_m values as that in the nodules. Because a stop codon is located 15 base pairs upstream of the N-35 initiation codon, it appears that a fusion protein with LacZ was not made, but reinitiation occurred due to the presence of a putative Shine-Dalgarno sequence in the appropriate region. The size of the N-35 polypeptide made in E. coli is identical to that present in soybean nodules and is able to assemble into a tetrameric holoenzyme with the same molecular weight as the native uricase. Thus, the presence of peroxisomes does not appear to be essential for the proper assembly of the holoenzyme in E. coli. These data also indicate that posttranslational modifications or membrane transport are not essential either for the assembly of N-35 into a holoenzyme or for the activity of uricase.     

Spatial distribution of predators and prey affect biological control of twospotted spider mites by Phytoseiulus persimilis in greenhouses

We evaluated the effects of predator release pattern and prey distribution on rate of suppression of the twospotted spider mite, Tetranychus urticae Koch (Acari, Tetranychidae) and visual damage to the ornamental plant, Impatiens wallerana Hook.f., in a greenhouse. Sixteen impatiens plants were arranged in a square and infested with the same total number of spider mites distributed either evenly (equal numbers on all plants) or clumped (divided equally among the 4 central plants), simulating a “hot spot.” The predatory mite, Phytoseiulus persimilis Athias-Henriot, was released at a 1:4 predator:prey ratio based on total spider mites in the experimental unit, but the pattern of release was either even or clumped, which simulated broadcast or point-release strategies, respectively. Nine days after predator release, spider mite populations were reduced in all treatments, but only in the clumped pest-clumped predator treatment were spider mites undetectable. Poorest pest suppression occurred in the clumped spider mite-even predator treatment. Eighteen days after predator release, spider mites were eliminated in all treatments, but a reduction in average plant damage occurred only in treatments in which the predator release pattern matched the spider mite distribution (i.e., even-even or clumped-clumped) with the greatest reduction in the even-even treatment. Results suggest that there is an advantage to releasing predators in “hot spots” provided that the recommended predator:prey ratio is maintained within infested patches. If more uniform predator releases are planned, overall predator numbers need to be kept sufficiently high so that the predator:prey ratio of 1:4 shown to prevent damage on impatiens is achieved in higher-density spider mite patches.     

Effect of gibberellic Acid on the plasticity and elasticity of Avena stem segments

Extensibility characteristics of Avena stem segments treated with gibberellic acid (GA) were investigated in living internodes using a microgrowth method and in partially extracted cell walls subjected to Instron extensometer analysis. Both techniques showed that treatment with GA greatly increases internodal plasticity, but has virtually no effect on internodal elasticity. The increase in plasticity occurred 1 to 2 hours after the initiation of hormone treatment, which is similar to the time of onset of GA-enhanced growth and cell wall synthesis. Cycloheximide was shown to inhibit the effect of GA on plasticity.     

Population dynamic of the extinct European aurochs: genetic evidence of a north-south differentiation pattern and no evidence of post-glacial expansion

Background

Various evolutionary models have been proposed to interpret the fate of paralogous duplicates, which provides substrates on which evolution selection could act. In particular, domestication, as a special selection, has played important role in crop cultivation with divergence of many genes controlling important agronomic traits. Recent studies have indicated that a pair of duplicate genes was often sub-functionalized from their ancestral functions held by the parental genes. We previously demonstrated that the rice cell-wall invertase (CWI) gene GIF1 that plays an important role in the grain-filling process was most likely subjected to domestication selection in the promoter region. Here, we report that GIF1 and another CWI gene OsCIN1 constitute a pair of duplicate genes with differentiated expression and function through independent selection.

Results

Through synteny analysis, we show that GIF1 and another cell-wall invertase gene OsCIN1 were paralogues derived from a segmental duplication originated during genome duplication of grasses. Results based on analyses of population genetics and gene phylogenetic tree of 25 cultivars and 25 wild rice sequences demonstrated that OsCIN1 was also artificially selected during rice domestication with a fixed mutation in the coding region, in contrast to GIF1 that was selected in the promoter region. GIF1 and OsCIN1 have evolved into different expression patterns and probable different kinetics parameters of enzymatic activity with the latter displaying less enzymatic activity. Overexpression of GIF1 and OsCIN1 also resulted in different phenotypes, suggesting that OsCIN1 might regulate other unrecognized biological process.

Conclusion

How gene duplication and divergence contribute to genetic novelty and morphological adaptation has been an interesting issue to geneticists and biologists. Our discovery that the duplicated pair of GIF1 and OsCIN1 has experienced sub-functionalization implies that selection could act independently on each duplicate towards different functional specificity, which provides a vivid example for evolution of genetic novelties in a model crop. Our results also further support the established hypothesis that gene duplication with sub-functionalization could be one solution for genetic adaptive conflict.     

Predaceous Behavior and Life History of Odontopharynx longicaudata (Diplogasterida)

The behavior of a California isolate of the predaceous nematode, Odontopharynx longicaudata de Man, was studied in water agar culture. When feeding on an Acrobeloides sp. the predator completed its life cycle in 13 to 14 days at 25 C. Optimum temperature for reproduction of the predator was 25 C, few individuals survived at 10 C, and 30 C was lethal. Males were necessary for reproduction, and at 25 C the sex ratio was about 1:1. All postembryonic stages were voracious feeders. A single female predator consumed 30 individuals of another Acrobeloides sp. in 1.5 days. Juveniles must feed in order to complete their development. Three modes of feeding were observed depending on the prey selected. A high degree of prey selectivity occurred; 6 of 17 nematode prey species were readily consumed by the predator, but there was little or no feeding on the remaining 11 species. Predation percentage varied with prey species. Consumption of Anguina pacificae and the two Acrobeloides spp. was almost 100%, consumption of A. amsinckiae, Pratylenchus vulnus, and Trichodorus sp. was 70-78%. Difference in final predator population densities was obtained after feeding on the two species of Acrobeloides. Final predator population densities increased linearly with increasing inoculum levels of the first Acrobeloides sp.     

Sugar homeostasis mediated by cell wall invertase GRAIN INCOMPLETE FILLING 1 (GIF1) plays a role in pre‐existing and induced defence in rice

Sugar metabolism and sugar signalling are not only critical for plant growth and development, but are also important for stress responses. However, how sugar homeostasis is involved in plant defence against pathogen attack in the model crop rice remains largely unknown. In this study, we observed that the grains of gif1, a loss‐of‐function mutant of the cell wall invertase gene GRAIN INCOMPLETE FILLING 1 (GIF1), were hypersusceptible to postharvest fungal pathogens, with decreased levels of sugars and a thinner glume cell wall in comparison with the wild‐type. Interestingly, constitutive expression of GIF1 enhanced resistance to both the rice bacterial pathogen Xanthomonas oryzae pv. oryzae and the fungal pathogen Magnaporthe oryzae. The GIF1‐overexpressing (GIF1‐OE) plants accumulated higher levels of glucose, fructose and sucrose compared with the wild‐type plants. More importantly, higher levels of callose were deposited in GIF1‐OE plants during pathogen infection. Moreover, the cell wall was much thicker in the infection sites of the GIF1‐OE plants when compared with the wild‐type plants. We also found that defence‐related genes were constitutively activated in the GIF1‐OE plants. Taken together, our study reveals that sugar homeostasis mediated by GIF1 plays an important role in constitutive and induced physical and chemical defence.     

Metal tolerance of an indigenous cyanobacterial strain, Lyngbya putealis

Response of an indigenous cyanobacterial strain (Lyngbya putealis) isolated from contaminated site to increasing levels of copper and cobalt was investigated in single metal systems. This cyanobacterial strain showed better response when the medium was spiked with metal. As compared to cobalt treatment, copper had more favorable effect. In single metal systems (copper or cobalt), metal treatments positively effected the cyanobacterial growth as indicated by higher concentration of the primary and accessory photosynthetic pigment (chlorophyll and phycobiliproteins), and biomass production at 0.5 mg/L (M_0.5) as compared to that at control (M₀). Exopolymer production (exopolysaccharides and extracellular proteins) too tended to increase significantly in response to both copper and cobalt in L. putealis and found to be maximum at metal concentration M_2.0. This species also showed increased accumulation of starch and carbohydrates in presence of metal (copper or cobalt) at M_0.1. But the overall response was better for copper as compared to cobalt in single metal systems for almost all the studied parameters which show that the strain offered good protection against copper but was sensitive to cobalt.