Nowadays, the oral use of probiotics is widespread. However, the safety profile with the use of live probiotics is still a matter of debate. Main risks include: Cases of systemic infections due to translocation, particularly in vulnerable patients and pediatric populations; acquisition of antibiotic resistance genes; or interference with gut colonization in neonates. To avoid these risks, there is an increasing interest in non-viable microorganisms or microbial cell extracts to be used as probiotics, mainly heat-killed (including tyndallized) probiotic bacteria (lactic acid bacteria and bifidobacteria). Heat-treated probiotic cells, cell-free supernatants, and purified key components are able to confer beneficial effects, mainly immunomodulatory effects, protection against enteropathogens, and maintenance of intestinal barrier integrity. At the clinical level, products containing tyndallized probiotic strains have had a role in gastrointestinal diseases, including bloating and infantile coli—in combination with mucosal protectors—and diarrhea. Heat-inactivated probiotics could also have a role in the management of dermatological or respiratory allergic diseases. The reviewed data indicate that heat-killed bacteria or their fractions or purified components have key probiotic effects, with advantages versus live probiotics (mainly their safety profile), positioning them as interesting strategies for the management of common prevalent conditions in a wide variety of patients´ characteristics.

Erwinia amylovora, a Gram negative bacteria of the Enterobacteriaceae family, is the causal agent of fire blight, a devastating plant disease affecting a wide range of host species within Rosaceae and a major global threat to commercial apple and pear production. Among the limited number of control options currently available, prophylactic application of antibiotics during the bloom period appears the most effective. Pathogen cells enter plants through the nectarthodes of flowers and other natural openings, such as wounds, and are capable of rapid movement within plants and the establishment of systemic infections. Many virulence determinants of E. amylovora have been characterized, including the Type III secretion system (T3SS), the exopolysaccharide (EPS) amylovoran, biofilm formation, and motility. To successfully establish an infection, E. amylovora uses a complex regulatory network to sense the relevant environmental signals and coordinate the expression of early and late stage virulence factors involving two component signal transduction systems, bis-(3′-5′)-cyclic di-GMP (c-di-GMP) and quorum sensing. The LPS biosynthetic gene cluster is one of the relatively few genetic differences observed between Rubus- and Spiraeoideae-infecting genotypes of E. amylovora. Other differential factors, such as the presence and composition of an integrative conjugative element associated with the Hrp T3SS (hrp genes encoding the T3SS apparatus), have been recently described. In the present review, we present the recent findings on virulence factors research, focusing on their role in bacterial pathogenesis and indicating other virulence factors that deserve future research to characterize them.

AlthoughAnoxybacillusandGeobacillus, two genera of thermophilic bacteria close to the genusBacillus, have only been described recently, the number of species in these genera has increased rapidly. Four thermophilic, lipolytic strains (DR01, DR02, DR03 and DR04) isolated from a hot spring in Veracruz (Mexico), which could not be identified phenotypically, were subjected to 16S rRNA gene sequence analysis. Three strains were identified as belonging to the genusAnoxybacillus, but strain DR03 was identified asGeobacillus pallidus. This result led us to perform a phylogenetic analysis of the generaAnoxybacillusandGeobacillusbased on 16S rRNA gene sequences from all the type strains of these genera. Phylogenetic trees showed three major clusters,Anoxybacillus–Geobacillus tepidamans,Geobacillussensu strictoandGeobacillus pallidus, while the 16S rRNA gene sequences ofG. pallidus(DR03 and the type strain) showed low similarity to sequences ofAnoxybacillus(92.5–95.1 %) andGeobacillus(92.8–94.5 %) species, as well as toBacillus subtilis(92.2–92.4 %). In addition,G. palliduscould be differentiated fromAnoxybacillusandGeobacilluson the basis of DNA G+C content and fatty acid and polar lipid profiles. From these results, it is proposed thatGeobacillus pallidusshould be classified in a novel genus, for which we propose the nameAeribacillus, asAeribacillus pallidusgen. nov., comb. nov. The type strain ofAeribacillus pallidusis H12^T(=ATCC 51176^T=DSM 3670^T=LMG 19006^T).

FiveAeromonasstrains (848T^T, 93M, 431E, 849T and 869N), which were isolated from bivalve molluscs and were recognized previously by numerical taxonomy as members of an unknownAeromonastaxon, were subjected to a polyphasic taxonomic study. DNA–DNA hybridization experiments showed that DNA of strain 848T^Twas <70 % similar (27–45 %) to that of the type/reference strains of the currentAeromonashybridization groups (HGs), but 93 % similar to that of strain 93M. The DNA G+C content of the five strains ranged from 59·0 to 59·4 mol%. 16S rRNA gene sequence analysis confirmed that the strains belonged to the genusAeromonasand showed high similarity toAeromonas encheleia. Amplified fragment length polymorphism fingerprinting clustered the novel strains in a homogeneous group with low genotypic relatedness to otherAeromonasspecies. Useful phenotypic features for differentiating the five isolates from otherAeromonasspecies include their negative reactions in tests for indole production, lysine decarboxylase, gas from glucose and starch hydrolysis. From the results of this study, the nameAeromonas molluscorumsp. nov. is proposed for these strains, with the type strain 848T^T(=CECT 5864^T=LMG 22214^T).

A polyphasic study was performed to determine the taxonomic position of twoAeromonasstrains, 665N and 868E^T, isolated from bivalve molluscs, that could not be identified at the species level in a previous numerical taxonomy study. The DNA G+C content of these isolates was 62.3 and 62.6 mol%, respectively. Sequence analysis of the 16S rRNA gene showed that the two new strains were closely related to members of the genusAeromonas. Fluorescence amplified fragment length polymorphism fingerprinting revealed that strains 665N and 868E^Tclustered together with a similarity of 78 % but did not cluster with any of theAeromonasgenomospecies. DNA–DNA hybridization experiments revealed a high level of relatedness between the two new isolates (76 %) but low levels of relatedness between these and phylogenetically most closely relatedAeromonasgenomospecies (30–44 %). Useful tests for the phenotypic differentiation of strains 665N and 868E^Tfrom other mesophilicAeromonasspecies included those for gas from glucose, lysine decarboxylase, Voges–Proskauer reaction, acid froml-arabinose, hydrolysis of aesculin and utilization ofl-lactate. On the basis of genotypic and phenotypic evidence, strains 665N and 868E^Tare considered to represent a novel species of the genusAeromonas, for which the nameAeromonas bivalviumsp. nov. is proposed. The type strain is 868E^T(=CECT 7113^T=LMG 23376^T).

During the taxonomic investigation of cold-adapted bacteria from samples collected in the Antarctic area of the South Shetland Islands, one Gram-reaction-negative, psychrotolerant, aerobic bacterium, designated strain M1^T, was isolated from marine sediment collected on Deception Island. The organism was rod-shaped, catalase- and oxidase-positive and motile by means of a polar flagellum. This psychrotolerant strain grew at temperatures ranging from −4 °C to 34 °C. Phylogenetic studies based on 16S rRNA gene sequences confirmed that Antarctic isolate M1^T was a member of the genus Pseudomonas and was located in the Pseudomonas fragi cluster. 16S rRNA gene sequence similarity values were >98 % between 13 type strains belonging to the Pseudomonas fluorescens lineage. However, phylogenetic analysis of rpoD gene sequences showed that strain M1^T exhibited high sequence similarity only with respect to Pseudomonas psycrophila (97.42 %) and P. fragi (96.40 %) and DNA–DNA hybridization experiments between the Antarctic isolate M1^T and the type strains of these two closely related species revealed relatedness values of 58 and 57 %, respectively. Several phenotypic characteristics, together with the results of polar lipid and cellular fatty acid analyses, were used to differentiate strain M1^T from related pseudomonads. Based on the evidence of this polyphasic taxonomic study, strain M1^T represents a novel species, for which the name Pseudomonas deceptionensis sp. nov. is proposed. The type strain is M1^T ( = LMG 25555^T = CECT 7677^T).