The role of non-specific serum opsonins in thein vitro interaction (adherence) between peritoneal macrophages of newborn precolostral piglets and rough strain ofEscherichia coli

The role of non-antibody, natural opsonins in sera of newborn, precolostral piglets for the early phase of phagocytosis (adhesion) of roughEscherichia coli to peritoneal macrophages of these animals, was studied. Suspensions of macrophages, incubated together with bacteria in the presence or absence of piglet serum opsonins, were submitted to differential centrifugation to enable the separation of macrophage-associated bacteria (i.e. opsonized) from unopsonized, free bacteria in the supernatant. It was found that native piglet sera having no detectable antibody activity toEscherichia coli, do possess significant opsonic activity,i.e. they enhanced thein vitro adherence of roughEscherichia coli to macrophages. Furthermore, this activity could be removed by procedures or substances known to inactivate the complement by different mechanisms: heating for 30 min at 56°C, addition of EDTA, absorption of sera by zymosan, addition of complement inhibitors phosphomannan and carrageenin. These results are interpreted as further evidence for the presence of complement-dependent serum opsonins to roughEscherichia coli in sera of newborn precolostral piglets.     

Characterization of the bactericidal action of precolostral piglet and calf sera against gram negative enteric bacteria in rough phase

The bactericidal activities of precolostral piglet and calf sera against two Gram negative bacteria (a rough strain,Escherichia coli 16, and a non-rough strain,Shigella shigae) were studied. It was found that the bactericidal factors againstEscherichia coli 16 can be closely correlated with the complement (C′) factors which participate in the hemolysis of sheep erythrocytes sensitized with amboceptor. No specific factor againstEscherichia coli 16 could be absorbed from the serum. The bactericidal action againstShigella appeared to require other factor(s) in addition to the C′ system. This factor(s) could be removed from native or heat inactivated serum by absorption withShigella and not by absorption with other bacterial strains. Evidence is presented which suggests that this factor is not similar to the classical 19S type antibody. Results in this study indicate that the limiting factors in the bactercidal action againstEscherichia coli 16 andShigella shigae are different.     

Studies on the phagocytic activity of the reticuloendothelial system (RES) to rough and smoothEscherichia coli in young conventional and germfree guinea pigs

The functional (phagocytic) capacity of the reticuloendothelial system (RES) of young conventional and germfree guinea pigs was studied using thein vivo blood clearance test of living bacteria (rough and smoothEscherichia coli). It was found that as previously shown in newborn germfree piglets, the smooth strain was taken up from the blood stream of germfree guinea pigs very slowly whereas roughEscherichia coli was phagocytosed effectively. The inability of the RES of germfree guinea pigs to phagocytose the smooth strain is not due to a functional incapability of phagocytic cells, but it reflects rather the lack of serum opsonins to this strain. This was demonstrated in experiments in which smooth bacteria, sensitized prior to injection into the blood circulation with specific antiserum, were phagocytosed as effectively as the rough strain. It is assumed that effective phagocytosis of rough strain is due to the presence of non-specific opsonins (e.g. components of the complement system). In young conventional guinea pigs both strains,i.e. smooth and rough, were taken up from the blood stream very effectively thus indicating that sufficient levels of serum opsonins for both strains were present. This fact could be correlated with the finding that in sera of conventional guinea pigs haemagglutinating antibodies to both strains ofEscherichia coli could be detected, whereas in sera of young germfree guinea pigs, no antibodies to usedEscherichia coli strain were found. The importance of serum opsonins for effective phagocytosis of bacteria by RE cellsin vivo is discussed.     

Lysis of lyophilizedEscherichia coli cells with egg-white lysozyme without ethylenediaminetetraacetic acid

A simple method of lysis of lyophilized cells ofEscherichia coli is described, using egg-white lysozyme in the absence of ethylenediaminetetraacetic acid (EDTA).     

The inhibition of bactericidal activity of sera of newborn germ-free piglets to roughEscherichia coli by yeast mannan

The yeast phosphomannan (PM) derived fromHansenula capsulata strain exerts an inhibitory effect on thein vitro bactericidal activity of fresh sera of newborn, colostrum-deprived germ-free piglets to rough strains ofEscherichia coli (S-16 and Lilly). The experiments presented indicate that the PM function probably takes place at the C1 level. The inhibitory effect of PM does not occur provided bacteria are sensitized by specific antiserum prior to exposure to piglet serum. The antibody which was responsible for removal of PM blockade was of 19S nature, 2-mercaptoethanol-sensitive and can be absorbed by heat inactivated bacteria (roughEscherichia coli) or inhibited by addition of soluble somatic antigen (endotoxin) obtained from the same strain ofEscherichia coli (rough). The possible mechanism of inhibition of bactericidal activity by PM is discussed. This investigation was done in the Laboratory of Dr. M. A. Leon, Pathology Research, St. Luke's Hospital, Cleveland, Ohio, U.S.A.     

Histone-induced changes of protein synthesis inEscherichia coli

The addition of histone to the medium in the logarithmic phase of growth ofEscherichia coli influences alkaline phosphatase synthesis in two ways: it delays initiation of derepression of synthesis of the enzyme by about 60–80 min and it inhibits its synthesis. The inhibitory effect persists even after removing histone from the medium. In stationary-phase of growth the inhibitory effect of histone is obliterated. From an analysis of the initial kinetics of derepressed alkaline phosphatase synthesis and from previous results (?trbáňová-Ne?inováet al., 1972) it is concluded that histone added toEscherichia coli cells interferes with the synthesis of mRNA for alkaline phosphatase.     

Effect of glucose starvation on the melting points of DNA following UV irradiation ofEscherichia coli 15 T−U−his−

The effect of glucose starvation during the pre-irradiation period on the UV resistance and on the DNA melting points was investigated. The radio-resistance ofEscherichia coli 15 T^?U^? his ^? increases markedly with the length of starvation. The DNA melting point of an exponentially growing culture is decreased by a dose of 500 erg/mm² by 3 C. The same dose does not affect the melting point of DNA in a prestarved culture.     

Analysis of theilv-linked genes that determine the morphology ofEscherichia coli Cells

The genetic location ofwee relative tocya was measured by cotransduction with a Tn5 insertion inilv. These experiments locatedwee at 84.8 min in the standardEscherichia coli map. Mutations incya andwee give rise to morphological changes, coccal morphology incya and short rods inwee, suggesting that both may be involved in the pathways of cell elongation. Addition of cAMP to the cultures reverted thecya but not thewee phenotype. Cells ofE. coli in the absence of thewee gene product were, contrary to what has been described forcya cells, as sensitive to mecillinam as in its presence. These results suggested that the action of Wee on elongation is exerted at a level different from that of adenyl cyclase.     

Chemotaxis toward amino acids inBacillus subtilis

Quantitative measurement of positive chemotaxis inBacillus subtilis was performed by means of adaption of the procedure used in studies withEscherichia coli. The motility ofB. subtilis was optimal in the presence of an exogeneous energy source and a nonionic detergent,e. g. Tween 80 or Brij-36. B. subtilis is chemotactic toward the commonly occurringL-amino acids except arginine, lysine, aspartate and glutamate. No chemotactic response was observed towardD-amino acids. Threshold, optimal response and peak concentration were determined. Chemotaxis toward glutamine was optimal at pH 6-7 and a temperature of 32°C. The maximum response toward a particular attractant was presumably influenced by the aerotactic behavior ofB. subtilis.     

Role of CD11b/CD18 in priming of human leukocytes by endotoxin glycoforms from Escherichia coli

The primary objective of this study was to determine the role of β2 integrin α-subunit (CD11b) in the mechanism of human polymorphonuclear leukocyte (PML) priming by S or Re endotoxin glycoforms from Escherichia coli for fMLP-induced respiratory burst. Similar priming activity of S and Re endotoxin glycoforms for fMLP-induced reactive oxygen species (ROS) generation from primed PML was found. Anti-CD11b antibodies (clone ICRF 44) as well as isotypematched immunoglobulin G1 (clone MOPC-21) do not influence the fMLP-induced ROS generation from unprimed PML. Antibodies against CD11b do not change fMLP-induced ROS generation from endotoxin-primed PML as well. The involvement of different isoforms of Fcγ receptors in fMLP-induced ROS generation from activated PML is proposed.     

Effect of lowered incubation temperatures on nucleic acid and protein synthesis by a mesophilic and a psychrophilic bacterium

The authors studied changes in the synthesis of nucleic acids (RNA, DNA) and protein by a mesophilic strain ofEscherichia coli B and a psychrophilic strain ofPseudomonas fluorescens at a low incubation temperature giving tenfold prolongation of the generation time. It was found that lowering the incubation temperature was followed by an increase in the intracellular nucleic acid content during the lag phase and the phase of accelerated growth, in which maximum nucleic acid (NA) values were reached. As a result, the total NA level in the cell also remained relatively high during further proliferation, when the increase in NA (particularly RNA) slows down at low incubation temperatures. Proteosynthesis, however, fell in the mesophilic culture. The smaller effect of a lowered temperature on DNA biosynthesis was manifested specifically in the lag phase ofEscherichia coli, in which disproportion developed between the amount of DNA (which was synthesized at a relatively higher rate) and RNA; this was afterwards equalized by a temporary break in DNA production. Pronounced differences in the given types of biosynthesis were found only in the mesophilic culture, while at suboptimal temperatures the metabolism of the psychrophilic strain slowed down but no marked changes occurred.     

The effect of Sa and MiniSa plasmids on the induction of plant crown galls and hairy roots byAgrobacterium tumefaciens andAgrobacterium rhizogenes

The Inc-W group plasmid Sa or its derivative MiniSa were introduced into two strains ofAgrobacterium tumefaciens with Ti plasmids, one strain ofA. tumefaciens with the Ri plasmid and oneA. rhizogenes strain with the Ri plasmid. The effect was similar in allAgrobacterium strains. The pSa suppressed fully the virulence ofAgrobacterium strains (i.e. their ability to induce tumor growths - crown galls or hairj⁷ roots) inKalanchoe plants and carrot root slices. The MiniSa plasmid caused only a slight decrease of the frequency and size of tumor growths induced. The mechanism of suppression of virulence by the Sa plasmid inAgrobacterium tumefaciens andAgrobacterium rhizogenes seems to be similar.     

Stability of the hybrid plasmid pIM138 and its curing by some eliminating agents

Hybrid plasmid pIM138 was constructed by insertion of a chromosomal fragment with the threonme operon fromEscherichia coli into the pBR322 vector. Molar mass of pIM138 was 2.8 Mg/mol. Heteroduplexes between pBR322 vector and pIM138 hybrid DNA molecules were prepared. The hybrid plasmid shows a high stability against the curing effect of rifampicin and clorobiocm inE. coli SK1590thr host.