Cannibalism as an interacting phenotype: precannibalistic aggression is influenced by social partners in the endangered Socorro Isopod (Thermosphaeroma thermophilum).

Models for the evolution of cannibalism highlight the importance of asymmetries between individuals in initiating cannibalistic attacks. Studies may include measures of body size but typically group individuals into size/age classes or compare populations. Such broad comparisons may obscure the details of interactions that ultimately determine how socially contingent characteristics evolve. We propose that understanding cannibalism is facilitated by using an interacting phenotypes perspective that includes the influences of the phenotype of a social partner on the behaviour of a focal individual and focuses on variation in individual pairwise interactions. We investigated how relative body size, a composite trait between a focal individual and its social partner, and the sex of the partners influenced precannibalistic aggression in the endangered Socorro isopod, Thermosphaeroma thermophilum. We also investigated whether differences in mating interest among males and females influenced cannibalism in mixed sex pairs. We studied these questions in three populations that differ markedly in range of body size and opportunities for interactions among individuals. We found that relative body size influences the probability of and latency to attack. We observed differences in the likelihood of and latency to attack based on both an individual's sex and the sex of its partner but found no evidence of sexual conflict. The instigation of precannibalistic aggression in these isopods is therefore a property of both an individual and its social partner. Our results suggest that interacting phenotype models would be improved by incorporating a new conditional ψ, which describes the strength of a social partner's influence on focal behaviour.

Nonadditive effects of group membership can lead to additive group phenotypes for anti-predator behaviour of guppies, Poecilia reticulata.

Nonadditive effects of group membership are generated when individuals respond differently to the same social environment and may alter predictions about how behavioural evolution will occur. Despite this importance, the relationship between an individual's behaviour in two different social contexts and how reciprocal interactions among individuals within groups influence group behaviour are poorly understood. Guppy anti-predator behaviour can be used to explore how individuals behaviourally respond to changes in social context. Individuals from two strains were tested for response to a model predator alone and in groups to evaluate how individuals alter their behaviour in response to social context and how group phenotype relates to individual behaviour. Nonadditive effects of group membership were detected for a number of behaviours, revealing that the effect of being in a group differed among individuals. These nonadditive effects, however, yielded an additive group phenotype. That is, the average behaviour of the group was equal to the average of its parts, for all behaviours in both strains. Such an additive group phenotype may have resulted because all individuals within a group respond to the specific social environment provided by the other members of their group.

Survival of insect pathogenic and human clinical isolates of Photorhabdus luminescens in previously sterile soil.

Most characterized strains of the bacterium Photorhabdus luminescens are symbionts of entomopathogenic nematodes, whereas other strains have been isolated from human clinical specimens. The ability of P. luminescens strains to survive and grow in soil has received limited attention, with some studies indicating these bacteria have little or no ability to persist in soil. Survival and (or) growth of P. luminescens strains in previously sterilized soil, and examination of different soil amendments on their numbers in soil, have not been previously reported. Entomopathogenic P. luminescens (ATCC 29999) and a human clinical isolate (ATCC 43949) were introduced into a soil that had been sterilized by autoclaving, with or without different soil amendments, and bacterial numbers were estimated over time by viable plate count. In the previously sterilized soil receiving no exogenous amendments, numbers fell drastically over a week's time, followed by an increase in numbers by day 30. Treatments involving the addition of calcium carbonate and gelatin or casamino acids to soil usually resulted in higher bacterial numbers. For some sampling dates and soil treatments, there were statistically significant differences between the numbers of the two bacterial strains recovered from soil. The two strains of P. luminescens used in this study were able to survive and grow after being inoculated into previously sterilized soil.

Effects of a lignin peroxidase-expressing recombinant, Streptomyces lividans TK23.1, on biogeochemical cycling and the numbers and activities of microorganisms in soil.

A recombinant actinomycete, Streptomyces lividans TK23.1, expressing a pIJ702-encoded extracellular lignin peroxidase gene cloned from the chromosome of Streptomyces viridosporus T7A, was released into soil in flask- and microcosm-scale studies to determine its effects on humification and elemental cycling and on the numbers, types, and activities of microorganisms native to the soil. Strain TK23.1 had been shown previously to transiently increase the rate of organic carbon mineralization in soil via an effect that was recombinant specific and particularly significant in nonsterile soils already possessing an active microflora. The results of this study confirmed the previous findings and showed that additional effects were measurable upon release of the recombinant strain TK23.1 into unamended soil and into soil amended with lignocellulose. In addition to a transient enhancement of carbon mineralization, the recombinant affected soil pH, the rate of incorporation of carbon into soil humus fractions, nitrogen cycling, the relative populations of some microbial groups, and also certain soil enzyme activities. Whereas the survival or persistence in soil of the recombinant TK23.1 strain and that of its parent, TK23, were similar, the observed effects on microbial numbers, types, and activities were recombinant specific and did not occur when the parental strain was released into soil. All of the measured effects were transient, generally lasting for only a few days. While the effects were statistically significant, their ecological significance appears to be minimal. This is the first report showing that a recombinant actinomycete can affect the microbial ecology of soil in ways that can be readily monitored by using a battery of microbiological, enzymological, and chemical assays.

Cloning and expression of a lignin peroxidase gene from Streptomyces viridosporus in Streptomyces lividans.

A lignin peroxidase gene was cloned from Streptomyces viridosporus T7A into Streptomyces lividans TK64 in plasmid pIJ702. BglII-digested genomic DNA (4-10 kb) of S. viridosporus was shotgun-cloned into S. lividans after insertion into the melanin (mel+) gene of pIJ702. Transformants expressing pIJ702 with insert DNA were selected based upon the appearance of thiostrepton resistant (tsrr)/mel-colonies on regeneration medium. Lignin peroxidase-expressing clones were isolated from this population by screening of transformants on a tsr-poly B-411 dye agar medium. In the presence of H2O2 excreted by S. lividans, colonies of lignin peroxidase-expressing clones decolorized the dye. Among 1000 transformants screened, 2 dye-decolorizing clones were found. One, pIJ702/TK64.1 (TK64.1), was further characterized. TK64.1 expressed significant extracellular 2,4-dichlorophenol (2.4-DCP) peroxidase activity (= assay for S. viridosporus lignin peroxidase). Under the cultural conditions employed, plasmidless S. lividans TK64 had a low background level of 2.4-DCP oxidizing activity. TK64.1 excreted an extracellular peroxidase not observed in S. lividans TK64, but similar to S. viridosporus lignin peroxidase ALip-P3, as shown by activity stain assays on nondenaturing polyacrylamide gels. The gene was located on a 4 kb fragment of S. viridosporus genomic DNA. When peroxidase-encoding plasmid, pIJ702.LP, was purified and used to transform three different S. lividans strains (TK64, TK23, TK24), all transformants tested decolorized poly B-411. When grown on lignocellulose in solid state processes, genetically engineered S. lividans TK64.1 degraded the lignocellulose slightly better than did S. lividans TK64. This is the first report of the cloning of a bacterial gene coding for a lignin-degrading enzyme.

Assessing the risks of releasing recombinant Streptomyces in soil.

Streptomyces spp. are soil microorganisms that are important in decomposition of organic matter in soil. Genetic exchange among Streptomyces species is known to occur readily both on agar and in soil in the laboratory and evidence indicates that transfer of genes from released recombinant Streptomyces to native soil streptomycetes also occurs. Minimal data are available on the environmental effects of such gene transfer.

Floc Formation by Azospirillum lipoferum Grown on Poly-beta-Hydroxybutyrate.

Azospirillum lipoferum RG6xx was grown under conditions similar to those resulting in encystment of Azotobacter spp. A. lipoferum produced cells of uniform shape when grown on nitrogen-free beta-hydroxybutyrate agar. Cells accumulated poly-beta-hydroxybutyrate and often grew as chains or filaments that eventually lost motility and formed capsules. Within 1 week, vegetative A. lipoferum inocula were converted into microflocs arising from filaments or chains. Cells within microflocs were pleomorphic, contained much poly-beta-hydroxybutyrate, and were encapsulated. Some cells had a cystlike morphology. Up to 57% of the dry weight of encapsulated flocs was poly-beta-hydroxybutyrate, whereas vegetative cells grown in broth with combined nitrogen had only 3% of their dry weight as poly-beta-hydroxybutyrate. Neither encapsulated cells in flocs nor nonencapsulated vegetative cells were significantly desiccation resistant. Under starvation conditions (9 days) only 25% of encapsulated cells remained viable, whereas vegetative cells multiplied severalfold. In short-term germination experiments with encapsulated flocs, nitrate, ammonium, and soil extract promoted formation of motile vegetative cells. Most cells in treatments lacking combined nitrogen eventually depleted their visible poly-beta-hydroxybutyrate reserves without germinating. The remaining cells retained the reserve polymer and underwent size reduction.

Nitrous oxide production by organisms other than nitrifiers or denitrifiers.

Heterotrophic bacteria, yeasts, fungi, plants, and animal breath were investigated as possible sources of N(2)O. Microbes found to produce N(2)O from NO(3) but not consume it were: (i) all of the nitrate-respiring bacteria examined, including strains of Escherichia, Serratia, Klebsiella, Enterobacter, Erwinia, and Bacillus; (ii) one of the assimilatory nitrate-reducing bacteria examined, Azotobacter vinelandii, but not Azotobacter macrocytogenes or Acinetobacter sp.; and (iii) some but not all of the assimilatory nitrate-reducing yeasts and fungi, including strains of Hansenula, Rhodotorula, Aspergillus, Alternaria, and Fusarium. The NO(3)-reducing obligate anaerobe Clostridium KDHS2 did not produce N(2)O. Production of N(2)O occurred only in stationary phase. The nitrate-respiring bacteria produced much more N(2)O than the other organisms, with yields of N(2)O ranging from 3 to 36% of 3.5 mM NO(3). Production of N(2)O was apparently not regulated by ammonium and was not restricted to aerobic or anaerobic conditions. Plants do not appear to produce N(2)O, although N(2)O was found to arise from some damaged plant tops, probably due to microbial growth. Concentrations of N(2)O above the ambient level in the atmosphere were found in human breath and appeared to increase after a meal of high-nitrate food.