Interactions of Chaperonin with a Weakly Active Anthranilate Synthase from the Aphid Endosymbiont <Emphasis Type="Italic">Buchnera aphidicola</Emphasis>

The endosymbiotic bacterium Buchnera provides its aphid host with essential amino acids. Buchnera is typical of intracellular symbiotic and parasitic microorganisms in having a small effective population size, which is believed to accelerate genetic drift and reduce the stability of gene products. It is hypothesized that Buchnera mitigates protein instability with an increased production of the chaperonins GroESL. In this paper, we report the expression and functional analysis of trpE, a plasmid-borne fast-evolving gene encoding the tryptophan biosynthesis enzyme anthranilate synthase. We overcame the problem of low enzyme stability by using an anthranilate synthase-deficient mutant of E. coli as the expression host and the method of genetic complementation for detection of the enzyme activity. We showed that the Buchnera anthranilate synthase was only weakly active at the temperature of 26°C but became inactive at the higher temperatures of 32°C and 37°C and that the coexpression with chaperonin genes groESL of E. coli enhanced the function of the Buchnera enzyme. These findings are consistent with the proposed role of groESL in the Buchnera–aphid symbiosis.     

Differences in the high-temperature tolerance of <Emphasis Type="Italic">Aphis craccivora</Emphasis> (Hemiptera: Aphididae) on cotton and soybean: implications for ecological niche switching among hosts

To forecast the effects of climate change and extreme temperature events on insect population dynamics, the high-temperature tolerance of insects must be taken into account. We compared the life-history characteristics of cowpea aphid (Aphis craccivora Koch) across different temperature regimes on two different host plants, soybean (a preferred host) and cotton (a non-preferred host). Most demographic parameters were superior for the aphid on soybean than on cotton. Temperatures affected aphid development more on cotton than on soybean. The intrinsic rate of increase, reproduction rate, number of progeny per adult, and longevity were significantly higher on soybean than on cotton for the same temperature regime. Temperatures that fluctuated to extreme levels caused a rapid decline in each of these parameters for aphids fed on cotton, but not for those fed on soybean. To our knowledge, this is the first report to note that the high-temperature tolerance of A. craccivora is host-specific (cotton vs. soybean). Our findings may partly explain the observed niche switching of the cowpea aphid (Aphis craccivora) from cotton to soybean at the beginning of summer when the temperature goes up in the Xinjiang cotton-growing zone (Northwest China). This host mediation of high-temperature tolerance in aphids should be taken into account when modeling population dynamics under the influence of global warming, host adaptation, and the risk analysis of alien pest invasions.     

Importance of early arrival of adult <Emphasis Type="Italic">Harmonia axyridis</Emphasis> for control of <Emphasis Type="Italic">Aphis spiraecola</Emphasis> on apple

The biological control of aphid populations may only be possible when natural enemies arrive soon after aphid colonization. This study was done to identify how quickly adult Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) need to arrive at newly established spirea aphid [Aphis spiraecola Patch (Homoptera: Aphididae)] colonies on apple (Malus domestica Borkh.) to provide population control. A total of 100 newly established spirea aphid colonies were caged in an experimental apple orchard in West Virginia, USA. A single adult H. axyridis was added to each of ten caged colonies at day 0, 5, 10, 15 and 20 days after caging. An additional ten caged colonies were opened for exposure to natural levels of predation at each of the treatment intervals as a control. The single H. axyridis eliminated the aphid colonies significantly more quickly than natural predation for up to ten days after colony establishment. The probability of an aphid colony producing alates was significantly lower in the presence of a single H. axyridis adult than when exposed to natural predation for the first ten days. Adult H. axyridis beetles are capable of completely controlling individual spirea aphid colonies on apple only if they are abundant enough to find colonies within one week of colony establishment.     

Biotransformation of racemic diisophorone by <Emphasis Type="Italic">Cephalosporium aphidicola</Emphasis> and <Emphasis Type="Italic">Neurospora crassa</Emphasis>

Racemic diisophorone (500 mg) was converted by Cephalosporium aphidicola and Neurospora crassa over 10 days at 25 °C to 8β-hydroxydiisophorone in yields of 10% (52 mg) and 20% (103 mg), respectively. The structure was established by IR, specific rotation, mass spectral, 1D and 2D-NMR studies.Revisions requested 2 March 2005 and 21 April 2005; Revisions received 8 April 2005 and 10 May 2005     

Functional response and life history parameters of <Emphasis Type="Italic">Apanteles taragamae</Emphasis>, a larval parasitoid of <Emphasis Type="Italic">Maruca vitrata</Emphasis>

The legume pod borer Maruca vitrata Fabricius (Lepidoptera: Crambidae) is a serious pest of cowpea in West-Africa. The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) that originates from Taiwan is a potential candidate for biological control of M. vitrata. We investigated under laboratory conditions the functional response of the parasitoid by offering each experienced female 10, 20, 30 and 40 larvae of M. vitrata. We studied the influence of different host larval ages on the development, longevity, sex ratio, lifetime fecundity and parasitization rate of the wasp. In a comparative study, we also investigated the life history of A. taragamae and M. vitrata at different temperatures in the range of 20–30°C. The parasitoid successfully parasitized two- and three-day-old host larvae (first and second instars). Younger larvae (one-day-old) were parasitized to a lesser extent, and only males developed in them. Older larvae were not parasitized, partly because of defensive host behaviour. The success of parasitization was positively correlated with the density of two-day-old M. vitrata larvae. Parasitoid developmental time and longevity decreased with increasing temperature. The intrinsic rate of population increase (r _m ) exhibited an optimum curve with a maximum at 24–28°C. For the host M. vitrata, r _m was maximal at temperatures of 26–30°C. The data are discussed in the context of the potential of A. taragamae for biological control of M. vitrata.     

Chilling-induced changes of vacuolar proton pumps in hypocotyls of <Emphasis Type="Italic">Vigna unguiculata</Emphasis>

Vigna unguiculata (cowpea) is a legume adapted to high temperatures and is sensitive to low temperatures. Temperature is one of the limiting factors of growth and yield for many crops but its effect on cowpea metabolism is not known. We investigated the effect of chilling on activity of vacuolar proton pumps (V-ATPase and V-PPase) and their protein content in tonoplast vesicles of cowpea hypocotyls. Seedlings grown for 7 days at 10 or 4°C were used for experiments. Chilling treatment at 10 or 4°C markedly suppressed growth of cowpea seedlings. Following chilling at 10 and 4°C, activity of both proton pumps and the relative amount of V-PPase and subunit A of V-ATPase were significantly increased. Both substrate hydrolysis and H⁺ transport activities of V-PPase remained at relatively high levels during chilling treatment. For V-ATPase, treatment at 10°C for 6 days increased the ATP hydrolysis activity. However, the H⁺ transport activity of the enzyme was increased when treated for 4 days but was markedly decreased when treated for 6 days. Our results provide evidence for different regulation for these vacuolar proton pumps, indicating that V-PPase is the more stable proton pump throughout chilling stress.     

The tyrosine <Emphasis Type="Italic">O</Emphasis>-prenyltransferase SirD catalyzes <Emphasis Type="Italic">O</Emphasis>-, <Emphasis Type="Italic">N</Emphasis>-, and <Emphasis Type="Italic">C</Emphasis>-prenylations

Recently, the prenyltransferase SirD was found to be responsible for the O-prenylation of tyrosine in the biosynthesis of sirodesmin PL in Leptosphaeria maculans. In this study, the behavior of SirD towards phenylalanine/tyrosine and tryptophan derivatives was investigated. Product formation has been observed with 12 of 19 phenylalanine/tyrosine derivatives. It was shown that the alanine structure attached to the benzene ring and an electron donor, e.g., OH or NH₂, at its para-position are essential for the enzyme activity. Modifications were possible both at the side chain and the benzene ring. Enzyme products from seven phenylalanine/tyrosine derivatives were isolated and characterized by MS and NMR analyses including HSQC and HMBC and proven to be O- or N-prenylated derivatives at position C4 of the benzene rings. K _M values of six selected derivatives were found in the range of 0.10–0.68 mM. Catalytic efficiencies (K _cat/K _M ) were determined in the range of 430–1,110 s⁻¹·M⁻¹ with l-tyrosine as the best substrate. In addition, 7 of 14 tested tryptophan analogs were also accepted by SirD and converted to C7-prenylated derivatives, which was confirmed by comparison with products obtained from enzyme assays using a 7-dimethylallyltryptophan synthase 7-DMATS from Aspergillus fumigatus.     

Colony growth and dispersal in the ant-tended aphid, <Emphasis Type="Italic">Aphis craccivora</Emphasis> Koch,and the non-ant-tended aphid, <Emphasis Type="Italic">Acyrthosiphon pisum</Emphasis> Harris,under the absence of predators and ants

To elucidate the potential for colony growth and the dispersal of aphids in relation to the ant attendance, the mobility, tolerance of starvation, colony growth, and dispersal were examined in the ant-tended Aphis craccivora Koch and the non-ant-tended Acyrthosiphon pisum Harris under the absence of predators and ants. The increase of the dispersal rate with density was more conspicuous in Ac. pisum than Ap. craccivora. The success rate of dispersal was higher in Ac. pisum than Ap. craccivora. These results would be derived from the higher ability of dispersal by walking in Ac. pisum than Ap. craccivora. The longer legs, higher walking speed, and stronger tolerance of starvation in Ac. pisum might result in a higher ability of dispersal by walking. These traits may have developed in relation to non-ant attendance, because Ac. pisum aphids frequently escape from natural enemies by dropping from the host plant. On the other hand, Ap. craccivora have not developed morphological and behavioral traits concerning dispersal by walking, because increasing colony size without dispersal is likely to be advantageous for ant attraction. Escaping behaviors of Ap. craccivora from natural enemies have not been well developed due to the ant’s defense against natural enemies. The proportion of alatae in Ap. craccivora was higher than in Ac. pisum instead of a lesser ability for dispersal by walking in Ap. craccivora. The differences in ant attendance have been influenced in the development of morphological and behavioral traits concerning the dispersal ability, and then, different potentials for reproduction and dispersal have developed in ant-tended aphids and non-ant-tended aphids.     

<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> in Poland and Japan is nodulated by <Emphasis Type="Italic">Mesorhizobium amorphae</Emphasis> strains

Robinia pseudoacacia microsymbionts from plants growing in Poland and Japan were evaluated for phylogeny and taxonomic position by genomic approach. Based on the comparative analyses of atpD (368 bp) and dnaK (573 bp) gene sequences as well as 16S rDNA restriction analysis (RFLP-16S rDNA), R. pseudoacacia microsymbionts were identified as Mesorhizobium strains. In dnaK and atpD gene phylograms R. pseudoacacia nodulators formed robust, monophyletic clusters with Mesorhizobium species with the nucleotide sequence similarity of 91–98% and 90–98%, respectively. The classification of R. pseudoacacia rhizobia to the genus Mesorhizobium was also supported by amplified 16S rDNA restriction analysis. The studied bacteria formed common clusters with Mesorhizobium species, and their DNA patterns were identical or nearly identical to Mesorhizobium genus strains. When DNA-DNA hybridization was performed, the total DNA of the representative R. pseudoacacia rhizobia exhibited 51–75% relatedness to DNA of Mesorhizobium amorphae ICMP15022 strain and below 41% to DNA of other Mesorhizobium species. These results showed that R. pseudoacacia and M. amorphae belong to the same genomospecies. The G+C content of DNA of R. pseudoacacia two microsymbionts was 59.7 and 60.6 mol% compared to 61–64 mol% across M. amorphae strains.     

Population dynamics of a maternally-transmitted <Emphasis Type="Italic">Spiroplasma</Emphasis> infection in <Emphasis Type="Italic">Drosophila hydei</Emphasis>

A maternally-inherited spiroplasma endosymbiont of Drosophila hydei does not exert apparent phenotypes on both sexes of its host and is prevalent in natural populations of D. hydei. Our previous experiments using a laboratory stock of D. hydei revealed that low temperatures (such as 15°C and 18°C) dramatically lower the vertical transmission rates of this spiroplasma. Therefore, we hypothesized that, in temperate regions, the infection frequencies may decrease in cool seasons but increase in the summer season. To clarify the temporal population dynamics of the spiroplasma infection, D. hydei were collected from two Japanese populations in 2006–2008 from May to early August, representing the only period when a number of D. hydei are collectable in Japan, and examined for spiroplasma infection. Within each year, the frequency of spiroplasma infection fluctuated considerably in both populations. Consistent with our hypothesis, the infection frequency showed an increasing trend in both populations in 2007. However, the data in 2006 and 2008 did not show consistent patterns of increase. The population dynamics of spiroplasma infection may be affected but not critically determined by temperature. Moreover, despite the fluctuation within each year, the infection frequencies seemed to be stable across the years. The frequencies of spiroplasma infection in D. hydei populations may be stabilized by multiple factors. One of these factors may involve a context-dependent positive effect of spiroplasma on the fitness of D. hydei, as was recently observed in laboratory experiments.     

Proteomic analysis of <Emphasis Type="Italic">Psychrobacter</Emphasis><Emphasis Type="Italic"> cryohalolentis</Emphasis> K5 during growth at subzero temperatures

It is crucial to examine the physiological processes of psychrophiles at temperatures below 4°C, particularly to facilitate extrapolation of laboratory results to in situ activity. Using two dimensional electrophoresis, we examined patterns of protein abundance during growth at 16, 4, and −4°C of the eurypsychrophile Psychrobacter cryohalolentis K5 and report the first identification of cold inducible proteins (CIPs) present during growth at subzero temperatures. Growth temperature substantially reprogrammed the proteome; the relative abundance of 303 of the 618 protein spots detected (∼31% of the proteins at each growth temperature) varied significantly with temperature. Five CIPs were detected specifically at −4°C; their identities (AtpF, EF-Ts, TolC, Pcryo_1988, and FecA) suggested specific stress on energy production, protein synthesis, and transport during growth at subzero temperatures. The need for continual relief of low-temperature stress on these cellular processes was confirmed via identification of 22 additional CIPs whose abundance increased during growth at −4°C (relative to higher temperatures). Our data suggested that iron may be limiting during growth at subzero temperatures and that a cold-adapted allele was employed at −4°C for transport of iron. In summary, these data suggest that low-temperature stresses continue to intensify as growth temperatures decrease to −4°C.     

Sexual reproduction of the brooding sponge <Emphasis Type="Italic">Rhopaloeides odorabile</Emphasis>

Sexual reproduction of Rhopaloeides odorabile, a common Great Barrier Reef sponge, was quantified using histological sections from samples collected over two reproductive seasons. Rhopaloeides odorabile is viviparous and gonochoristic with a male biased sex ratio (2.5:1). Commencement and cessation of gametogenesis coincides with rising and falling sea surface temperatures (≈24–29°C). Spermatogenesis occurs from October until January. Females initiate oogenesis in September with the asynchronous development of oocytes, embryos and larvae occurring within the brood chambers. A larval release period of 5–6 weeks occurs during January and February. The minimum size of reproductive individuals was 176 cm³ for females and 192 cm³ for males. The total reproductive output for both sexes shows a positive correlation with size. A relative reproductive output index quantified the maximum reproductive investment at approximately 1 and 3% of the total choanoderm for females and males, respectively, which represents a lower range of reproduction in comparison to other viviparous sponges. Low reproductive output in R. odorabile may be offset by an extended spawning period, alleviating the risk of releasing larvae in potentially adverse conditions via one synchronised spawning event and increasing overall larval survival.     

Double deletion of <Emphasis Type="Italic">dtsR1</Emphasis> and <Emphasis Type="Italic">pyc</Emphasis> induce efficient <Emphasis Type="SmallCaps">l</Emphasis>-glutamate overproduction in <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Corynebacterium glutamicum strains are used for the fermentative production of l-glutamate. Five C. glutamicum deletion mutants were isolated by two rounds of selection for homologous recombination and identified by Southern blot analysis. The growth, glucose consumption and glutamate production of the mutants were analyzed and compared with the wild-type ATCC 13032 strain. Double disruption of dtsR1 (encoding a subunit of acetyl-CoA carboxylase complex) and pyc (encoding pyruvate carboxylase) caused efficient overproduction of l-glutamate in C. glutamicum; production was much higher than that of the wild-type strain and ΔdtsR1 strain under glutamate-inducing conditions. In the absence of any inducing conditions, the amount of glutamate produced by the double-deletion strain ΔdtsR1Δpyc was more than that of the mutant ΔdtsR1. The activity of phosphoenolpyruvate carboxylase (PEPC) was found to be higher in the ΔdtsR1Δpyc strain than in the ΔdtsR1 strain and the wild-type strain. Therefore, PEPC appears to be an important anaplerotic enzyme for glutamate synthesis in ΔdtsR1 derivatives. Moreover, this conclusion was confirmed by overexpression of ppc and pyc in the two double-deletion strains (ΔdtsR1Δppc and ΔdtsR1Δpyc), respectively. Based on the data generated in this investigation, we suggest a new method that will improve glutamate production strains and provide a better understanding of the interaction(s) between the anaplerotic pathway and fatty acid synthesis.     

Effect of temperature on the life-history traits of <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) fed on <Emphasis Type="Italic">Panonychus ulmi</Emphasis>

The developmental rate and reproductive biology of Neoseiulus californicus, a generalist predator on spider mites and small insects, was investigated in the laboratory at five constant temperatures: 15, 20, 25, 30, and 34°C. The European red mite, Panonychus ulmi, an important pest in Korean apple orchards, was used as prey. Mean developmental time and adult longevity were inversely related to temperature from 15 to 30°C. Lifetime fecundity was greatest at 25°C, whereas daily fecundity was highest at 30°C. The sex ratio (female to male) was highest (0.77) at 25°C and lowest (0.67) at 34°C. Survivorship during immature development varied from 74.3 to 92.9%, with the lowest rate at 34°C. Life table parameters were analyzed and pseudo-replicates for the generation time (t _G ), the intrinsic rate of natural increase (r _m), finite rate of increase (λ), net reproductive rate (R ₀), and doubling time (t _D ) were generated using the Jackknife method. Generation time (t _G ) was lowest (10.7 days) at 34°C, R ₀ was highest (49.2) at 25°C, and both r _m (0.29) and λ (1.34) were highest at 30°C. In conclusion, the development and adult life-history traits obtained for N. californicus fed on P. ulmi indicated significant potential for biological control.     

Benzyladenine Promotes Flowering in <Emphasis Type="Italic">Doritaenopsis</Emphasis> and <Emphasis Type="Italic">Phalaenopsis</Emphasis> Orchids

Two experiments were performed to determine how application of the cytokinin benzyladenine (BA) influenced flowering in Doritaenopsis and Phalaenopsis orchid clones. In the first experiment, two vegetative orchid clones growing in 15-cm pots were transferred from a 28°C greenhouse that inhibited flowering to a 23°C greenhouse for flower induction (day 0). A foliar spray (0.2 L m⁻²) containing BA at 100, 200, or 400 mg L⁻¹ or 25, 50, or 100 mg L⁻¹ each of BA and gibberellins A₄ + A₇ (BA+GA) was applied on days 0, 7, and 14. Plants treated with BA alone at 200 or 400 mg L⁻¹ had a visible inflorescence 3–9 days earlier and had a mean of 0.7–3.5 more inflorescences and 3–8 more flowers per plant than nontreated plants. The application of BA+GA had no effect on inflorescence number and total flower number at the rates tested. In the second experiment, three orchid clones received a single foliar spray of BA at 200 mg L⁻¹ at six time points relative to time of transfer from 29°C to 23°C (−1, 0, +1, +2, +4, or +6 weeks). A separate group of plants received a BA application at week 0 but was maintained at 29°C. Inflorescence number was greatest in all three orchid clones when plants were treated with BA 1 week after the temperature transfer. Plants that were sprayed with BA and maintained at 29°C did not initiate inflorescences. The promotion of flowering by the application of BA suggests that cytokinins at least partially regulate inflorescence initiation of Doritaenopsis and Phalaenopsis, but its promotion is conditional and BA application cannot completely substitute for an inductive low temperature.     

Characteristics of <Emphasis Type="Italic">Phomopsis sclareae</Emphasis> obtained from sage (<Emphasis Type="Italic">Salvia officinalis</Emphasis>)

In the years 2004–2006 the species P. sclareae was isolated from sage stems showing the symptoms in the form of bark peeling off and breaking. On the basis of 5 isolates randomly chosen from the fungus population, morphology and the conditions of temperatures favourable for the most intensive growth and creation of the fungus infectious material were studied. The temperature of −6°C was viewed as unfavourable for the fungus growth, and that of 32°C was considered to prevent the formation of picnidia and conidia. The dynamic growth of the colonies and the formation of numerous picnidia and conidia were observed at the temperatures ranging from 20°C to 28°C.     

Low-temperature limitation of primary photosynthetic processes in Antarctic lichens <Emphasis Type="Italic">Umbilicaria antarctica</Emphasis> and <Emphasis Type="Italic">Xanthoria elegans</Emphasis>

Temperature response curves of chlorophyll a fluorescence parameters were used to assess minimum sub-zero temperature assuring functioning of photosynthetic photochemical processes in photosystem II (PS II) of Antarctic lichens. Umbilicaria Antarctica and Xanthoria elegans were measured within the temperature range from −20 to +10°C by a fluorometric imaging system. For potential (F _V/F _M) and actual (Φ _II) quantum yields of photochemical processes the minimum temperature was found to be between −10 and −20°C. Non-photochemical quenching (NPQ) of absorbed excitation energy increased with temperature drop reaching maximum NPQ at −15°C. Image analysis revealed intrathalline heterogeneity of chlorophyll a fluorescence parameters with temperature drop. Temperature response of Φ _II exhibited an S-curve with pronounced intrathalline differences in X. elegans. The same relation was linear with only limited intrathalline difference in U. antarctica. The results showed that Antarctic lichen species were well adapted to sub-zero temperatures and capable of performing primary photosynthesis at −15°C.     

Characterization of <Emphasis Type="Italic">Francisella</Emphasis> sp., GM2212, the first <Emphasis Type="Italic">Francisella</Emphasis> isolate from marine fish,Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>)

A Francisella sp., isolate GM2212^T, previously isolated from diseased farmed Atlantic cod Gadus morhua in Norway is characterized. The complete 16S rDNA, 16S–23S intergenic spacer, 23S rDNA, 23S–5S intergenic spacer, 5S rDNA, FopA, lipoprotein TUL4 (LpnA), malate dehydrogenase and a hypothetical lipoprotein (LpnB) is sequenced and compared with Francisella tularensis and Francisella philomiragia. All these sequences support a close relationship between GM2212^T and F. philomiragia. The bacterium grows at 10–25°C with an optimum at about 20°C, a temperature range clearly different from F. tularensis and F. philomiragia. GM2212^T is catalase-positive, indole positive, oxidase-negative, do not produce H₂S in Triple Sugar Iron agar, and does not hydrolyze gelatin, is resistant to erythromycin and susceptible to ceftazidime, the latter five characteristics separating it from F. philomiragia. Cysteine enhances growth. Acid is produced from d-glucose, maltose, sucrose (weak) but not from lactose or glycerol. GM2212^T grows on both MacConkey agar and in nutrient broth (6% NaCl). The bacterium is resistant to trimethoprim-sulfamethoxazole, penicillines, cefuroxime and erythromycin; but is susceptible to ceftazidime, tetracycline, gentamicin, ciprofloxacin. Based on the molecular and phenotypical characteristics, we suggest that this GM2212 isolate, may represent a new species of Francisella. Isolate GM2212^T (=CNCM I-3481^T = CNCM I-3511^T = DSM 18777^T).     

Actinomycetemcomitin: a new bacteriocin produced by <Emphasis Type="Italic">Aggregatibacter</Emphasis> (<Emphasis Type="Italic">Actinobacillus</Emphasis>) <Emphasis Type="Italic">actinomycetemcomitans</Emphasis>

Aggregatibacter (Actinobacillus) actinomycetemcomitans P_7–20 strain isolated from a periodontally diseased patient has produced a bacteriocin (named as actinomycetemcomitin) that is active against Peptostreptococcus anaerobius ATCC 27337. Actinomycetemcomitin was produced during exponential and stationary growth phases, and its amount decreased until it disappeared during the decline growth phase. It was purified by ammonium sulphate precipitation (30–60% saturation), and further by FPLC (mono-Q ionic exchange and Phenyl Superose hydrophobic interaction) and HPLC (C-18 reversed-phase). This bacteriocin loses its activity after incubation at a pH below 7.0 or above 8.0, following heating for 30 min at 45°C, and after treatment with proteolytic enzymes such as trypsin, α-chymotrypsin, and papain. Actinomycetemcomitin has a molecular mass of 20.3 KDa and it represents a new bacteriocin from A. actinomycetemcomitans.     

Temperature-dependent development and reproductive traits of <Emphasis Type="Italic">Tetranychus macfarlanei</Emphasis> (Acari: Tetranychidae)

Development and reproductive traits of Tetranychus macfarlanei Baker & Pritchard (Acari: Tetranychidae) were investigated on kidney bean, Phaseolus vulgaris L., at eleven constant temperatures. Tetranychus macfarlanei was able to develop and complete its life cycle at temperatures ranging from 17.5 to 37.5°C. At 15 and 40°C, a few eggs (2–4%) hatched but further development was arrested. Development from egg to adult was slowest at 17.5°C and fastest at 35°C for both females and males. Using Ikemoto and Takai’s linear model, the estimated lower developmental thresholds for egg-to-female adult, egg-to-male adult and egg-to-egg development were 12.9–13.0°C. The thermal constants for the respective stages were 110.85, 115.99 and 125.32 degree-days (DD). The intrinsic optimum temperatures (T _Φ) calculated by non-linear SSI model were determined as 24.4, 24.4 and 24.2°C for egg-to-female adult, egg-to-male adult and egg-to-egg development, respectively. The net reproductive rate (R ₀) was highest at 25°C (167.4 females per female) and lowest at 17.5°C (42.6 females per female). The intrinsic rate of natural increase, r _m, increased linearly with the rising of temperature from 0.102 at 17.5°C to 0.441 day⁻¹ at 35°C. These values suggested that T. macfarlanei could be growing quickly in response to increasing temperatures from 17.5 to 35°C and provide a basis for predicting its potential geographical range.