Relationship between steps in 8-anilino-1-naphthalene sulfonate (ANS) fluorescence and changes in the energized membrane state and in intracellular and extracellular adenosine 5'-triphosphate (ATP) levels following bacteriophage T5 infection of Escherichia coli

Global transcriptome and physiological responses of Acinetobacter oleivorans DR1 exposed to distinct classes of antibiotics

The effects of antibiotics on environment-originated nonpathogenic Acinetobacter species have been poorly explored. To understand the antibiotic-resistance mechanisms that function in nonpathogenic Acinetobacter species, we used an RNA-sequencing (RNA-seq) technique to perform global gene-expression profiling of soil-borne Acinetobacter oleivorans DR1 after exposing the bacteria to 4 classes of antibiotics (ampicillin, Amp; kanamycin, Km; tetracycline, Tc; norfloxacin, Nor). Interestingly, the well-known two global regulators, the soxR and the rpoE genes are present among 41 commonly upregulated genes under all 4 antibiotic-treatment conditions. We speculate that these common genes are essential for antibiotic resistance in DR1. Treatment with the 4 antibiotics produced diverse physiological and phenotypic changes. Km treatment induced the most dramatic phenotypic changes. Examination of mutation frequency and DNA-repair capability demonstrated the induction of the SOS response in Acinetobacter especially under Nor treatment. Based on the RNA-seq analysis, the glyoxylate-bypass genes of the citrate cycle were specifically upregulated under Amp treatment. We also identified newly recognized non-coding small RNAs of the DR1 strain, which were also confirmed by Northern blot analysis. These results reveal that treatment with antibiotics of distinct classes differentially affected the gene expression and physiology of DR1 cells. This study expands our understanding of the molecular mechanisms of antibiotic-stress response of environment-originated bacteria and provides a basis for future investigations.

Variation of the permeability of bacteriophage T4: analysis by use of a protein-specific probe for the T4 interior

The permeability of bacteriophage T4 and the change in T4 permeability caused by mutation to osmotic shock resistance are investigated here by quantification of the kinetics with which both a DNA-specific probe (ethidium) and a protein-specific probe [1,1'-bi(4-anilino)naphthalene-5,5'-di-sulfonic acid, or bis-ANS)] bind to T4. In the case of an osmotic shock-resistant mutant, T40s41, both ethidium and bis-ANS bind with first order kinetics. The first-order rate constant (k*) for both bis-ANS and ethidium is a function of anion type and concentration. Adenosine triphosphate, phosphate, bisulfite, sulfate, and acetate anions all reduce k* below the k* observed when chloride is the only anion. When chloride is the only anion at 25 degrees C, k* values for binding to T40s41 are orders of magnitude above k* values for binding to wild-type T4 (T4wt). At 25 degrees C, k* for T4wt is too small to measure but k* for T4wt increases at 50-55 degrees C to values approaching those measured for T40s41, without inactivating T4wt, when chloride is the only anion; during heating, T4wt is stabilized by both ethidium and bis-ANS. Binding to T4wt is reversible at 50-55 degrees C, but not at 25 degrees C. Equilibrium binding of bis-ANS to T40s41 reveals 112 +/- 24 sites per T4 capsid. Equilibrium binding of ethidium to T40s41 reveals both high- and low-affinity sites previously observed in the packaged DNA of other bacteriophages. The ATP-induced decrease in k* is not accompanied by a decrease in equilibrium binding. The following hypotheses are presented to explain the above data: (a) All detected bis-ANS binding sites on T4 are interior to the outer surface of T4. (b) The value of k* for both bis-ANS and ethidium is controlled at the port(s) of passage through the outer shell of the T4 capsid. (c) The anions present control k* values at the port(s) of entry, probably by controlling the size of this port. The effects on k* of phosphate explain the otherwise paradoxical observation [P. J. McCall and V. A. Bloomfield (1976) Biopolymers 15, 2323-2336] that in a phosphate buffer the permeabilities of T4wt and T40s41 are the same.

Alteration of active transport after bacteriophage T5 infection

Bacteriophage T5 absorption immediately followed by injection of the first-step-transfer DNA segment produces alterations in the bacterial membrane which reduce the uptake of amino acids and of o-nitrophenyl-beta-D-galactopyranoside. Concomitantly, intracellular ATP is hydrolyzed. The extent of inhibition of uptake and of ATP hydrolysis is cooperatively increased with the multiplicity of infection. Inhibition of active transport at a high multiplicity of infection (greater than 3) is also observed after the second step of DNA injection. In contrast, at low multiplicities of infection, phage proteins are able to enhance amino acid uptake. Infection of su- bacteria with amber mutants in the first-step-transfer DNA suggests that protein A1 is implicated in this enhancement.

Protein composition and extractability of lipid-modified membranes from Acholeplasma laidlawii

Membranes from acholeplasma laidlawii have been extracted with neutral detergents, which solubilize the proteins and lipids selectively, or with sodium deoxycholate, which gives an almost total solubilization. The amounts of individual proteins present in the detergent extracts of membranes with induced variations in lipid compositions were determined by crossed immunoelectrophoresis. Extraction with the neutral detergent Tween 20 showed that ionic lipids and the glucolipid diglucosyl diglyceride were enriched in the Tween extracts whereas the glucolipid monoglucosyl diglyceride (which cannot easily by accommodated in micelles for geometrical reasons) was enriched in the membrane residue. The amount of monoglucosyl diglyceride in the Tween 20 extracts increased when the content of this lipid was increased in the membrane, and protein D12 was also more easily extracted from membranes rich in monoglucosyl diglyceride. This was not correlated with an increase in the total amounts of D12 in the membrane (as analyzed by crossed immunoelectrophoresis after sodium deoxycholate solubilization), indicating that monoglucosyl diglyceride is involved in the anchoring of protein D12 in the membrane. The total amount of the flavoprotein T4a in the membrane was found to increase upon enhanced amounts of ionic membrane lipids. Furthermore, protein T4a was found to be increasingly extractable upon an increase in the amounts of unsaturated fatty acyl chains in the lipids. Several other proteins also displayed lipid-dependent extractabilities. These results support the hypothesis that for membrane proteins the extractability with neutral detergents and thus interactions with lipids are partly dependent upon the molecular shapes of the membrane lipid molecules. Thus, by use of these selective extraction procedures, information about protein-lipid interactions in the membrane was gained.

Fast responses of bacterial membranes to virus adsorption: a fluorescence study

After collision with their host cells, virus particles may remain mobile on cell surfaces until they become attached at firm binding sites. We propose that a virion will arrive within a typical median time at such a site, generating a membrane signal such as an increased membrane fluorescence in cells labeled with the voltage-sensitive dyes 8-anilino-1-naphthalene-sulfonate (Mg-salt) (ANS), N-phenylnaphthylamine (NPA), or 3,3'-dipentyl-2,2'-oxacarbocyanine (di-O-C5[3]). We found that the time span between virus adsorption and fluorescence response varies widely among phages and also depends on bacterial strain, metabolic state, and type of dye. di-O-C5[3]-labeled cells react within 1 sec to uncouplers such as carbonyl cyanide m-chlorophenylhydrazone (CCCP). Cells labeled with ANS and NPA react to CCCP in 4-6 sec. Bacteriophages T4, T5, chi, and BF23, added to ANS-labeled cells, change the fluorescence in 9-15 sec. T-even ghosts cause a response at identical times. Baseplate-defective phage mutant T412- and isolated adsorption organelles of smaller viruses fail to cause an effect. di-O-C5[3]-labeled cells respond to T4 at a multiplicity of infection greater than or equal to 40 within 1 sec. A longer time (8 sec) is required at lower multiplicities. The receptor-degrading phages epsilon 15, epsilon 34, c 341, and K29 need the longest time (1 min for ANS) to cause a fluorescence increase. We suggest that the delayed fluorescence response is concomitant with the surface "walk" of the virion, which is terminated at an injection site. T4 tail sheath contraction coincides with the onset of the membrane fluorescence response.