Role of the Host Cell in Bacteriophage Morphogenesis: Effects of a Bacterial Mutation on T4 Head Assembly

In certain bacterial mutants, called groE, T4 phage head assembly is blocked specifically, implying that the host plays a direct role in head assembly. The block occurs early in the assembly process at the level of action of T4 gene 31.     

Trophic Dynamics and Niches of Salt Marsh Foraminifera

Energetic considerations of the growth of three species of littoralbenthic foraminifera, Allogromia laticollaris, Rosalina leei,and Spiroloculina hyalina, have been made on laboratory-grownpopulations. Under optimum laboratory conditions A. laticollarishas the greatest intrinsic rate of increase (r = 2.533 org/day);S. hyalina (r = 1.472 org/day), and R. leei (r = 0.272 org/day)being less fecund. The respiration rates of the three specieswere similar (0.5–4.5 µ1/mg body wt/hr) within thetemperature range (15–35 C) tested. The species studiedare selective feeders. Only 4-5 of 28 species of algae testedwere consumed in significant quantities (40-150 x 10⁸ g/foram/day).Although great numbers of bacteria were eaten, their biomasswas negligible when compared to the algae. The ecological growthefficiency (E_e) of the three species tested is highest in freshcultures (5-20%) and declines rapidly. Evidence suggests thatthe species studied are well adapted for the rapid changes inthe microbial community structure which take place throughoutthe summer, and that community stability and high rate of productivityare achieved through diversity.     

The Apoplastic Pathway of Transport to Salt Glands

The availability of the apoplastic route for ion transport tosalt glands was assessed by electron microscope examinationsand by the use of lanthanum as an electron-dense tracer to demarcatethe apoplast. The results show that this solute can reach thesalt glands via the apoplast and this observation is discussedin relation to current ideas concerning salt gland function.     

The Development and Structure of the Root-nodules of Myrica gale L. with Special Reference to the Nature of the Endophyte

The development and structure of the root nodules of Myricagale are described, and evidence advanced showing that theyrepresent modified lateral roots. Attempts at the isolationof the endophyte were unsuccessful, but on the basis of a cytologicalstudy of the nodules the author adheres to the view of someprevious investigators that the endophyte is actinomycetal.     

Comparative seed germination ecology of Austrostipa compressa and Ehrharta calycina (Poaceae) in a Western Australian Banksia woodland

Austrostipa compressa, a native ephemeral of southwest Western Australia was stimulated to germinate under a range of temperatures, in the presence of light, and exposure to smoke-water. This combination of environmental cues results in winter-maximum germination in immediate postfire and disturbed-soil environments of this Mediterranean-type climate. In contrast, Ehrharta calycina, an introduced perennial grass from southern Africa that has invaded Banksia woodlands, germinated under a wide range of temperature and light conditions, but showed no promotive response to smoke-water. Although A. compressa seeds tolerated heat shock better than E. calycina, the self-burial mechanism of A. compressa seeds ensures protection from fire. High-intensity fire could have a greater impact on E. calycina, as the seeds of this species tend to accumulate in the top of the soil profile where they are more susceptible to high temperatures. Although seeds of E. calycina are more susceptible to high temperatures, survival of mature individuals by postfire resprouting ensures continued survival in native woodlands. Estimates of soil seed bank densities showed extreme variability, but some recently burnt areas of the Yule Brook Botany Reserve contained up to 8000 seed m^?2 of A. compressa and nearly 75 000 seeds m^?2 of E. calycina. Viable soil seed bank densities of A. compressa are reduced with time-since-last fire, but areas of greater than 45 years since the last fire, still contained up to 119 seeds m^?2. In both species, only about half their soil seed bank germinates following fire, thus ensuring the potential for later recruitment. Massive soil seed populations of E. calycina in native Banksia woodlands pose a major problem to management of this plant community type.     

Postcranial remains of Baphetes and their bearing on the relationships of the Baphetidae (= Loxommatidae)

The first unequivocal postcranial remains of baphetids (= loxommatids) associated with skull roof and lower jaw material are reported from a specimen of Baphetes from the English Upper Carboniferous, Duckmantian. Characters of the mandible, including the incorporation in the symphysis of paired parasymphysial plates, permit the identification of a previously indeterminate jaw from the Langsettian (Westphalian A) of Nova Scotia, as baphetid. The postcranial remains include vertebrae, pectoral and pelvic limb and limb girdle elements that present a combination of unique characters extending the diagnosis of the family Baphetidae, together with plesiomophic and derived characters which suggest that baphetids are primitive stem group tetrapods.     

Isolation of microsatellite loci from the common buzzard,Buteo buteo (Aves: Accipitridae)

We isolated 56 common buzzard (Buteo buteo) microsatellite loci from (AC)_n‐ and (AAAG)_n‐enriched genomic libraries. Eleven loci were tested on 90 individuals from Eastern Westphalia in Germany, yielding two to 17 alleles per locus (average 5.7) and expected heterozygosities ranging from 0.11 to 0.93 (average 0.53). These highly variable microsatellite markers provide a powerful means for investigating population genetic diversity in the common buzzard, a little‐understood aspect of this widespread species.