The Bdellovibrio are miniature "living antibiotic" predatory bacteria which invade, reseal, and digest other larger Gram-negative bacteria, including pathogens. Nutrients for the replication of Bdellovibrio bacteria come entirely from the digestion of the single invaded bacterium, now called a bdelloplast, which is bound by the original prey outer membrane. Bdellovibrio bacteria are efficient digesters of prey cells, yielding on average 4 to 6 progeny from digestion of a single prey cell of a genome size similar to that of the Bdellovibrio cell itself. The developmental intrabacterial cycle of Bdellovibrio is largely unknown and has never been visualized "live." Using the latest motorized xy stage with a very defined z-axis control and engineered periplasmically fluorescent prey allows, for the first time, accurate return and visualization without prey bleaching of developing Bdellovibrio cells using solely the inner resources of a prey cell over several hours. We show that Bdellovibrio bacteria do not follow the familiar pattern of bacterial cell division by binary fission. Instead, they septate synchronously to produce both odd and even numbers of progeny, even when two separate Bdellovibrio cells have invaded and develop within a single prey bacterium, producing two different amounts of progeny. Evolution of this novel septation pattern, allowing odd progeny yields, allows optimal use of the finite prey cell resources to produce maximal replicated, predatory bacteria. When replication is complete, Bdellovibrio cells exit the exhausted prey and are seen leaving via discrete pores rather than by breakdown of the entire outer membrane of the prey.The predatory bacterium Bdellovibrio bacteriovorus invades and grows within the periplasmic space of another prey bacterium, hydrolyzing the interior of that prey bacterium to provide a quantized meal, growing into long elongated cells, and using those resources and not external nutrients (18). Although Bdellovibrio bacteria were discovered in 1962, their small size (0.25 by 1 m, compared to the more usual 1-by 3-m dimensions of a typical Escherichia coli cell) and the very nature of their growth within the periplasm of another bacterium has made their growth and development recalcitrant to live microscopic studies. (25) Thus, we have not been able to observe how exactly a single predatory Bdellovibrio cell makes use of the finite resources of a single prey cell (called a bdelloplast, once invaded) to grow and then manages to coordinate the departure of its progeny from that bdelloplast once prey resources are exhausted. The conundrum of predatory, intrabacterial growth by Bdellovibrio bacteria, which seems at odds with the conventions of typical binary fission of simple, nonpredatory bacteria in limitless culture media, has interested microbiologists since the 1960s (12,18,21).Early electron microscopic (EM) studies at time points throughout a predatory infection showed "attack-phase" Bdellovibrio cells entering prey by squeezing through a pore made in the outer membra...

Ozone (O3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (SA) synthesis. In pathogen-infected leaves, SA is synthesized via two pathways, involving phenylalanine or isochorismate. SA biosynthesis under O3 fumigation is not well understood. When we applied 14C-labeled benzoic acid (a precursor of SA in the pathway via phenylalanine) to O3-exposed tobacco leaves, it was effectively metabolized to SA. However, the activity and mRNA level of isochorismate synthase (ICS) were not increased. In contrast, ICS activity was increased in O3-exposed Arabidopsis thaliana L. These results suggest that SA is synthesized via benzoic acid from phenylalanine in O3-exposed tobacco leaves but via isochorismate in Arabidopsis. Ethylene is a plant hormone that promotes leaf damage in O3-exposed plants. During O3 exposure, transgenic plants with a phenotype of reduced O3-induced ethylene production accumulated less SA than did wild-type plants. O3 increased the activity of phenylalanine ammonia-lyase (PAL) and the transcript levels of the chorismate mutase (CM) and PAL genes in wild-type tobacco, but their induction was suppressed in the transgenic plants. These results indicate that ethylene promotes SA accumulation by regulating the expression of the CM and PAL genes in O3-exposed tobacco.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is a unique enzyme that associates with the pSer/Thr-Pro motif and catalyzes cis-trans isomerization. We identifiedIn good agreement with these in vitro data, Pin1 knock-out mice exhibited impaired insulin signaling with glucose intolerance, whereas adenoviral gene transfer of Pin1 into the ob/ob mouse liver mostly normalized insulin signaling and restored glucose tolerance. In addition, it was also demonstrated that Pin1 plays a critical role in adipose differentiation, making Pin1 knock-out mice resistant to diet-induced obesity. Importantly, Pin1 expression was shown to be up-regulated in accordance with nutrient conditions such as food intake or a high-fat diet. Taken together, these observations indicate that Pin1 binds to IRS-1 and thereby markedly enhances insulin action, essential for adipogenesis.

We compared the physiological and molecular responses of two Arabidopsis accessions, Col-0 and Ws-2, to ozone (O 3 ) exposure. Observation of visible injury as well as ion-leakage analysis demonstrated clear differences between the O 3 -tolerant accession Col and the O 3 -sensitive accession Ws. RNA-blot analysis showed that O 3 -induced increases in mRNA levels of several ethylene-inducible genes and a salicylic acid-inducible gene were substantially higher in Ws than in Col. The time-course of induction of various mRNA levels shows that the expression of ethylene-inducible genes was rapidly, and more strongly, induced by O 3 in Ws than in Col, suggesting that Ws exhibits higher ethylenesignaling. Both the level of mRNA for an O 3 -inducible 1-aminocyclopropane-1-carboxylate synthase and the level of ethylene generation after 3 h of O 3 -exposure were higher in Ws than in Col. O 3 -induced leaf damage was attenuated by pretreatment with ethylene biosynthesis-and signaling-inhibitors, indicating that ethylene signaling is required for O 3 -induced leaf injury in Ws. On the other hand, an ethylene-overproducing mutant of Col, eto1-1, displayed significantly increased O 3 -in-duced leaf injury compared to wild type plants. These results indicate that the difference in O 3 sensitivity is dependent on the difference in ethylene production rate between these two accessions. Finally, we investigated the relationship between the degree of leaf damage and the level of ethylene evolution in 20 different Arabidopsis accessions. Based on the result, the accessions were classified into four types. However, most of them showed significant correlation between the ethylene production level and the degree of leaf injury, suggesting that ethylene signaling is an important factor in the natural variety of O 3 sensitivity among Arabidopsis accessions.

A novel ozone-sensitive mutant was isolated from Arabidopsis T-DNA tagging lines. This mutant revealed severe foliar injury and higher ethylene emission than the wild type under ozone exposure. The ozone-induced injury and ethylene emission were suppressed by pretreatment with aminoethoxyvinyl glycine, an inhibitor of ethylene biosynthesis, both in this mutant and wild-type plants. Pretreatment with methyl-jasmonate (MeJA) at 10 micro M, however, suppressed the ozone-induced ethylene emission and foliar injury only in the wild-type plants. This mutant was less sensitive to jasmonate than the wild type, estimated by the MeJA-induced inhibition of root elongation and ozone-induced expression of AtVSP1, a jasmonate-inducible gene. Thus, this mutant was named oji1 (ozone-sensitive and jasmonate-insensitive 1). These results suggest that the ozone sensitivity of oji1 is caused by the increase in ozone-induced emission of ethylene as a result of low sensitivity to jasmonate, which plays defensive roles under stress conditions.