Expression in Bacillus subtilis of the gene for human urogastrone using synthetic ribosome binding sites

Summary A chemically synthesised gene coding for human urogastrone which was earlier cloned in E. coli (Smith et al. 1982) has now been cloned into expression vectors for Bacillus subtilis Two types of constructs have been made, one giving production of methionylurogastrone and the other giving rise to a methionyl-urogastrone- galactosidase fusion polypeptide facilitating quantification of expression levels.The ribosome binding sites used in the expression plasmids are synthetically made oligonucleotides residing on short restriction fragments to allow easy replacement by other ribosome binding sites.Using shuttle vectors and constitutive promoters from Bacillus phages 105 and SPP1, we were able to detect levels of expression amounting to a few thousand molecules per cell during logarithmic growth in both E. coli and B. subtilis.     

GENETIC DIVERSITY IN THE MONOECIOUS HYDROPHILE CERATOPHYLLUM (CERATOPHYLLACEAE)

This study surveys genetic variation in two clonal, monoecious, water-pollinated species that differ in their extent of sexuality and distributional range. Electrophoresis was used to quantify allozyme variability in 12 Wisconsin populations of the widespread Ceratophyllum demersum and the rare C. echinatum. Electrophoretic data indicate that populations of both species have low levels of sexual recombination, low levels of variation, and are structured genetically like inbreeding terrestrial plants. Ceratophyllum populations differ from “typical” clonal terrestrial plants by lower genetic diversity, lower proportions of multiclonal populations, and fewer genotypes per population. In two populations where sexual recombination is documented, heterozygosity is low with significant deficiencies. Monoecy in Ceratophyllum may be related to historical evolutionary factors, whereas vegetative reproduction has a greater influence on the genetic population structure of extant populations. The low genetic identity between C. demersum and C. echinatum supports their recognition as distinct species.     

Seasonal fluctuation of zooplankton populations in lower Delaware Bay

Quantitative zooplankton samples were obtained monthly or bi-monthly 15 times from June 1974 to May 1975 at three stations in lower Delaware Bay. Two 12-hour cruises were also conducted at one of the stations.Arthropods dominated the samples in terms of number of species and number of individuals. The number of zooplankton from surface samples ranged from 58/m³ in August to 21,092/ m³ in June, while bottom samples varied from 259/m³ in August to 30,395/ m³ in October. In general, larger concentrations of individuals were found in bottom samples.Only on three occasions did meroplankton exceed the holoplankton, and these occurred at the shallow water stations. Meroplankton comprised a larger percentage of the bottom samples than surface samples. Zoeae of Neopanope sayi and Uca sp. contributed mainly to the large proportion of meroplankton in July 1974, veligers of Mytilus edulis in January 1975, and nauplii of Balanus sp. in May 1975.Copepods were the largest component of the population throughout most of the year. At all stations and depths, Arctica tonsa dominated most of the summer samples. In the spring of 1975, A. tonsa was replaced by Centropages hamatus, Temora longicornis, and Pseudocalanus minutus.During the 12-hour cruises there were higher numbers of individuals in the bottom waters in the day with migration to surface waters in the afternoon and evening. Based on cluster analysis, five time-related assemblages were discerned: June, July–August, September–November, December, January–May. Comparison of Delaware Bay zooplankton with other estuarine systems indicated that the densities obtained locally were most similar to those reported in the York River, Virginia.     

Analysis of structural variations in a shallow estuarine deposit-feeding community

Changes in the structure of an estuarine, subtidal, benthic deposit-feeding community have been investigated. Three quantitative samples were taken within a grid 10 m on a side every four weeks from May, 1971 to July, 1973. Each sample was washed over a 250 μm sieve. Streblospio benedicti Webster, Capitella capitata (Fabricius), Heteromastus filiformis (Claparède), Potydora ligni Webster, and Paranais litoralis (Müller) were the five dominant species on the basis of their total abundance, percentage occurrence, and biological index value. Repeatable cycles in diversity were observed for Fager's scaled standard deviation and scaled information measure, as well as for Lloyd and Ghelardi's equitability, but not for the unsealed information theory measure. McNaughton's dominance index was strongly inversely correlated with all diversity measures. Graphical measures of lognormal skewness and normal kurtosis, as applied to Whittaker's dominance diversity curves, followed repeatable cycles, whereas normal skewness and lognormal kurtosis did not. A strong relationship between Fager's scaled standard deviation diversity, dominance, and the degree to which resources were being shared by the deposit-feeding segment of the community was suggested. A decrease in average niche width and average niche overlap was observed as the community developed during the period of strong larval recruitment.     

Potential causes of arrested succession in Kibale National Park, Uganda: growth and mortality of seedlings

Recent studies suggest that regeneration following large-scale disturbance in Kibale National Park, Uganda, is slow or possibly arrested. Here, data is provided on the growth and mortality of seedlings in the forest understory, treefall gaps, and in large gaps that suggest that this pattern of arrested succession can be attributed partially to the fact that this East African community lacks aggressive colonizing tree species. Growth and mortality rates were contrasted for seedlings of six tree species planted in the understory, small gaps, and large gaps for 36 months. Data suggest that species are adapted to gaps of particular sizes. For example, Uvariopsis congensis grew faster in the understory than in small gaps, whereas Warburgia ugandensis had the lowest mortality rate and highest growth rate in large gaps. Seedlings (n=170) of 15 species were transplanted to assess the response of the tree community to large gap conditions. The limited survival of seedlings in large gaps relative to the understory suggests that only a small proportion of the tree community in this forest regenerates best in gaps larger than those created by the collapse of a single tree. These findings differ from a number of studies conducted in other geographical regions, and suggests that tree communities differ with respect to the proportion of tree species adapted to gaps of particular sizes. This may relate to variation among regions in their history of disturbance and thus frequency of gap formation, size of gaps, and the duration of periods of release. Such variation could imply the existence of a corresponding pattern among tropical forests of differential vulnerability to human disturbance, which tends to create many large gaps.     

Contrasting strategies for wing‐moult and pre‐migratory fuelling in western and eastern populations of Common Whitethroat Sylvia communis

Trade‐offs between moult and fuelling in migrant birds vary with migration distance and the environmental conditions they encounter. We compared wing moult and fuelling at the northern and southern ends of migration in two populations of adult Common Whitethroats Sylvia communis. The western population moults most remiges at the breeding grounds in Europe (e.g. Poland) and migrates 4000–5000 km to western Africa (e.g. Nigeria). The eastern population moults all remiges at the non‐breeding grounds and migrates 7000–10 000 km from western Asia (e.g. southwestern Siberia) to eastern and southern Africa. We tested the hypotheses that: (1) Whitethroats moult their wing feathers slowly in South Africa, where they face fewer time constraints than in Poland, and (2) fuelling is slower when it coincides with moulting (Poland, South Africa) than when it occurs alone (Siberia, Nigeria). We estimated moult timing of primaries, secondaries and tertials from moult records of Polish and South African Whitethroats ringed in 1987–2017 and determined fuelling patterns from the body mass of Whitethroats ringed in all four regions. The western population moulted wing feathers in Poland over 55 days (2 July–26 August) at a varying rate, up to 13 feathers simultaneously, but fuelled slowly until departure in August–mid‐September. In Nigeria, during the drier period of mid‐February–March they fuelled slowly, but the fuelling rate increased three‐fold in April–May after the rains before mid‐April–May departure. The eastern population did not moult in Siberia but fuelled three times faster before mid‐July–early August departure than did the western birds moulting in Poland. In South Africa, the Whitethroats moulted over 57 days (2 January–28 February) at a constant rate of up to nine feathers simultaneously and fuelled slowly from mid‐December until mid‐April–May departure. These results suggest the two populations use contrasting strategies to capitalize on food supplies before departure from breeding and non‐breeding grounds.     

Population structure and evolution of the Bacillus cereus group

Representative strains of the Bacillus cereus group of bacteria, including Bacillus anthracis (11 isolates), B. cereus (38 isolates), Bacillus mycoides (1 isolate), Bacillus thuringiensis (53 isolates from 17 serovars), and Bacillus weihenstephanensis (2 isolates) were assigned to 59 sequence types (STs) derived from the nucleotide sequences of seven alleles, glpF, gmk, ilvD, pta, pur, pycA, and tpi. Comparisons of the maximum likelihood (ML) tree of the concatenated sequences with individual gene trees showed more congruence than expected by chance, indicating a generally clonal structure to the population. The STs followed two major lines of descent. Clade 1 comprised B. anthracis strains, numerous B. cereus strains, and rare B. thuringiensis strains, while clade 2 included the majority of the B. thuringiensis strains together with some B. cereus strains. Other species were allocated to a third, heterogeneous clade. The ML trees and split decomposition analysis were used to assign STs to eight lineages within clades 1 and 2. These lineages were defined by bootstrap analysis and by a preponderance of fixed differences over shared polymorphisms among the STs. Lineages were named with reference to existing designations: Anthracis, Cereus I, Cereus II, Cereus III, Kurstaki, Sotto, Thuringiensis, and Tolworthi. Strains from some B. thuringiensis serovars were wholly or largely assigned to a single ST, for example, serovar aizawai isolates were assigned to ST-15, serovar kenyae isolates were assigned to ST-13, and serovar tolworthi isolates were assigned to ST-23, while other serovars, such as serovar canadensis, were genetically heterogeneous. We suggest a revision of the nomenclature in which the lineage and clone are recognized through name and ST designations in accordance with the clonal structure of the population.