No trade‐offs in interspecific interference ability and predation susceptibility in newt larvae

Coexistence of species with similar requirements is allowed, among others, through trade‐offs between competitive ability and other ecological traits. Although interspecific competition is based on two mechanisms, exploitation of resources and physical interference, trade‐off studies largely consider only species’ ability to exploit resources. Using a mesocosm experiment, we examined the trade‐off between interference competition ability and susceptibility to predation in larvae of two newt species, Ichthyosaura alpestris and Lissotriton vulgaris. In the presence of heterospecifics, L. vulgaris larvae slowed somatic growth and developmental rates, and experienced a higher frequency of injuries than in conspecific environments which suggests asymmetrical interspecific interference. During short‐term predation trials, L. vulgaris larvae suffered higher mortality than I. alpestris. Larvae of the smaller species, L. vulgaris, had both lower interference and antipredator performance than the larger I. alpestris, which suggests a lack of trade‐off between interference competition ability and predator susceptibility. We conclude that interference competition may produce a positive rather than negative relationship with predation susceptibility, which may contribute to the elimination of subordinate species from common habitats.     

Bacteria Responsible for Mucilage-Layer Decomposition in Kona Coffee Cherries

The predominant microbial flora present during decomposition of the mucilage layer of Kona coffee cherries were gram-negative bacteria which fermented lactose rapidly. Cultures isolated from coffee cherries under-going fermentation included species of Erwinia, Paracolobactrum, and Escherichia. Unblemished cherry surfaces and coffee plantation soil also had a microflora containing a high proportion of bacteria belonging to these three genera. Of 168 isolates tested, the 44 strains capable of demucilaging depulped coffee cherries were all members of Erwinia dissolvens. Supernatant growth medium liquids, after removal of E. dissolvens cells, actively decomposed the mucilage layer of depulped cherries.     

Characterization of apoA-I-containing lipoprotein subpopulations secreted by HepG2 cells

Recent immunoaffinity studies demonstrate two populations of high density lipoprotein (HDL) particles: one contains both apolipoprotein (apo) A-I and A-II [Lp(A-I w A-II)], and the other contains apoA-I but no A-II [Lp(A-I w/o A-II)]. To investigate whether these two populations are derived from different precursors, we applied sequential immunoaffinity chromatography to study the lipoprotein complexes in HepG2 conditioned serum-free medium. The apparent secretion rates of apoA-I, A-II, E, D, A-IV, and lecithin:cholesterol acyltransferase (LCAT) were 4013 +/- 1368, 851 +/- 217, 414 +/- 64, 171 +/- 51, 32 +/- 14, and 2.9 +/- 0.7 ng/mg cell protein per 24 h, respectively (n = 3-5). Anti-A-II removed all apoA-II but only 39 +/- 5% (n = 5) apoA-I from the medium. These HepG2 Lp(A-I w A-II) also contained 31 +/- 1% (n = 5) of the apoD and 82 +/- 2% (n = 3) of the apoE in the medium. The apoE existed both as E and E-A-II complex. Lipoproteins isolated from the apoA-II-free medium by anti-A-I contained, besides apoA-I, 60 +/- 3% of the medium apoD and trace quantities of apoE. The majority of HepG2 apoA-IV (78 +/- 4%) (n = 3) and LCAT (85 +/- 6%) (n = 3) was not associated with either apoA-I or A-II. HepG2 Lp(A-I w A-II) contained relatively more lipids than Lp(A-I w/o A-II) (45 vs. 37%).(ABSTRACT TRUNCATED AT 250 WORDS)     

A gene-targeting suicide vector for Streptococcus bovis

J.D. BROOKER, D.K. LUM, A.M. THOMSON AND H.M. WARD. 1995. A gene-targeting suicide vector for Streptococcus bovis has been constructed using the Escherichia coli/Streptococcus shuttle plasmid, pMU1328, and a region derived from the broad host-range, Gram-positive transposon, Tn916. This suicide plasmid replicates autonomously in E. coli , but not in Strep, bovis or Strep, bovis Tn916. Under positive selection, the plasmid was shown to integrate into Strep, bovis Tn916 chromosomal DNA at a frequency of 3 × 10^-8cell^-1and was stably maintained for at least 100 generations in the absence of selection. This is the first report of a recombination system in ruminal bacteria. The ability to target genes, knock out specific functions or introduce novel genes into these micro-organisms will allow ruminal species to be manipulated and may eventually lead to improved animal production.     

Cholesterol esterification by lecithin-cholesterol acyltransferase in A-I-free plasma

Lecithin-cholesterol acyltransferase (LCAT) mass, activity and endogenous cholesterol esterification rate were measured in plasma and apolipoprotein A-I-free (A-I-free) plasma from two normolipidemic and two hyperlipidemic subjects, and from a patient with Tangier disease. A-I was removed from plasma by an anti-A-I immunosorbent. LCAT activity was measured using an exogenous substrate. The plasma LCAT concentration of the four non-Tangier subjects was 4.63 +/- 0.64 micrograms/ml (mean +/- S.D.); means of 26 +/- 7% of total LCAT mass and 22 +/- 11% of plasma LCAT activity were found in their A-I-free plasma. The plasma LCAT concentration of the Tangier subject was 1.49 micrograms/ml. About 95% of LCAT mass and all LCAT activity were found in the A-I-free plasma. Thus, the LCAT mass (1.4 micrograms/ml) and activity (43.1 nmol/h per ml) in Tangier A-I-free plasma were not significantly different from that found in the four non-Tangier A-I-free plasmas (mass = 1.21 +/- 0.44 micrograms/ml; activity: 27.3 +/- 18.4 nmol/h per ml). Although the LCAT activity per unit mass of the enzyme in plasma and A-I-free plasma were comparable (24.9 +/- 2.8 vs. 22.8 +/- 7.8 nmol/h per micrograms LCAT, n = 5), the plasma cholesterol esterification rate of A-I-free plasma from all subjects was lower than that found in plasma (7.5 +/- 2.7 vs. 13.0 +/- 3.8 nmol/h per micrograms LCAT). In conclusion, although A-I-containing lipoproteins are the preferred substrates of LCAT, other LCAT substrates and cofactors are found in A-I-free plasma along with LCAT. Thus, non-A-I-containing particles can serve as physiological substrates for cholesterol esterification mediated by LCAT.