Role for cheR of Vibrio fischeri in the Vibrio–squid symbiosis

Upon hatching, the Hawaiian squid Euprymna scolopes is rapidly colonized by its symbiotic partner, the bioluminescent marine bacterium Vibrio fischeri . Vibrio fischeri cells present in the seawater enter the light organ of juvenile squid in a process that requires bacterial motility. In this study, we investigated the role chemotaxis may play in establishing this symbiotic colonization. Previously, we reported that V. fischeri migrates toward numerous attractants, including N-acetylneuraminic acid (NANA), a component of squid mucus. However, whether or not migration toward an attractant such as squid-derived NANA helps the bacterium to localize toward the light organ is unknown. When tested for the ability to colonize juvenile squid, a V. fischeri chemotaxis mutant defective for the methyltransferase CheR was outcompeted by the wild-type strain in co-inoculation experiments, even when the mutant was present in fourfold excess. Our results suggest that the ability to perform chemotaxis is an advantage during colonization, but not essential.

Metallkomplexe mit funktionalisierten Schwefelliganden, XV [1]. Reaktionen von Platin(0)-Komplexen mit 1,2,4-Trithiolanen, 1,2,4,5-Tetrathianen, 1,2,3,5,6-Pentathiepanen sowie Thioketonen. Kristallstrukturanalyse von (Ph3P)2Pt(η2-Ph2C=S) / Metal Complexes of Functionalized Sulfur Containing Ligands, XV [1]. Reactions of Platinum(O) Complexes with 1,2,4-Trithiolanes, 1,2,4,5-Tetrathianes, 1,2,3,5,6-Pentathiepanes as well as Thioketones. X-Ray Structure Analysis of (Ph3P)2Pt(η2-Ph2C=S)

3,3,5,5-Tetraphenyl-1,2,4-trithiolane (1) reacts with twofold excess of (Ph3P)2Pt(η2-C2H4) (4) to give a 1:1 mixture of the complexes (Ph3P)2 (6a) and (Ph3P)2Pt(η2-Ph2C=S) (7a). Treatment of 3,3,6,6-tetraphenyl-1,2,4,5-tetrathiane (2) with a fourfold excess of 4 yields [Pt2(PPh3)4(μ-S)2] (8) and the platinum(O) compound 7a. The reaction of the 1,2,3,5,6- pentathiepane 3 with a fourfold excess of 4 affords a 1:1:1 mixture of 8, the platinum(O) complex 7b and the bis-thiolato platinum(II) complex 6b. The thioketone complexes 7a-c were formed in smooth reactions of 4 with the thioketones 5a-c. The molecular structure of (Ph3P)2Pt(η2-Ph2C=S) (7a) has been established by single-crystal X-ray analysis.

Breast-Feeding and Illness

To the Editor.— Holmes et al1 underestimated the association between breast-feeding and lowered illness rates. A separate comparison for their subgroup of more serious illnesses (lower respiratory tract infection, acute otitis media, gastroenteritis, meningitis—table 3) shows the following: For maternal education ≤11 years there were 53 such illnesses per 100 formula-fed infants (28 illnesses/53 infants) compared with 13 illnesses per 100 breast-fed infants (3/23), a fourfold excess. For maternal education ≥12 years formula-fed infants had 42 illnesses per 100 infants (raw data: 30 illnesses/71 infants) whereas the breast-fed infants had 27 illnesses per 100 infants (raw data: 28/104).

Structural Investigations on a Cell-Wall Lipopolysaccharide from Neisseria sicca

Lipopolysaccharide (LPS) prepared from Neisseria sicca in 1.5% yield contained D-glucose, D-glucosamine, D-galactosamine, 3-deoxyoctulosonic acid, protein, lipid A, and phosphate. The molecule was judged to be homogeneous as tested by free boundary electrophoresis. D-Galactosamine was associated exclusively with the polysaccharide portion of the molecule and was in fourfold excess of D-glucosamine. The latter hexosamine was primarily a constituent of the lipid A moiety in which it formed the backbone structure linked glycosidically 1 → 4. To this structure, fatty acids, principally β-hydroxymyristic acid and β-hydroxylauric acid, were linked along with phosphate groups. The D-glucosamine units in the polysaccharide portion of the LPS molecule were also attached by 1 → 4 glycosidic linkages. D-Galactosamine units did not survive the methylation procedures due presumably to the lack of acyl protecting groups on its amino groups. Methylation results showed that approximately one-third of the D-glucose units were nonreducing end groups, approximately one-third were linked α1 → 2, a small proportion was linked 1 → 4, and the remainder was branched through C-3, C-4, and C-6. Periodate oxidation results were in agreement with the structure proposed on the basis of the methylation data. The LPS of N. sicca was considerably simpler than that of N. perflava and lacked heptose, rhamnose, and ethanolamine components.

Interactions between the lysine-rich histone F1 and deoxyribonucleic acid

1. The interactions of the lysine-rich histone F1 with DNA have been studied at various histone to DNA ratios, in water and in the presence of uni- and bi-valent cations. In water only, histone F1, even in fourfold excess, is unable to precipitate all the DNA. In 0·14m-sodium chloride, 0·8mg. of histone F1 is required to precipitate 1mg. of DNA, whereas in 0·07m-magnesium chloride only 0·4mg. is required. 2. Bivalent cations are also shown to be more effective in dissociating the DNA–histone complex. Histone F1 can be selectively removed from deoxyribonucleoprotein with 0·1m-magnesium chloride. 3. The precipitation of DNA by histone F1 is a reversible process and the complex can be taken in and out of solution by changing the ionic environment. 4. The bearing of these results on the observed ability of various DNA–histone complexes to act as templates for RNA synthesis is discussed.