Antimicrobial Susceptibility of Persister Biofilm Cells of Bacillus cereus and Pseudomonas fluorescens

The present study evaluates the antimicrobial susceptibility of persister cells of Bacillus cereus and Pseudomonas fluorescens after their regrowth in suspension and as biofilms. Two conventional (benzalkonium chloride—BAC and peracetic acid—PAA) and two emerging biocides (glycolic acid—GA and glyoxal—GO) were selected for this study. Persister cells resulted from biofilms subjected to a critical treatment using the selected biocides. All biocide treatments developed B. cereus persister cells, except PAA that effectively reduced the levels of vegetative cells and endospores. P. fluorescens persister cells comprise viable and viable but non-culturable cells. Afterwards, persister cells were regrown in suspension and in biofilms and were subjected to a second biocide treatment. In general, planktonic cultures of regrown persister cells in suspension lost their antimicrobial tolerance, for both bacteria. Regrown biofilms of persister cells had antimicrobial susceptibility close to those regrown biofilms of biocide-untreated cells, except for regrown biofilms of persister P. fluorescens after BAC treatment, which demonstrated increased antimicrobial tolerance. The most active biocide against persister cells was PAA, which did not promote changes in susceptibility after their regrowth. In conclusion, persister cells are ubiquitous within biofilms and survive after critical biocide treatment. The descendant planktonic and biofilms populations showed similar properties as the original ones.

Effects of Bacillus amyloliquefaciens LFB112 on Growth Performance, Carcass Traits, Immune, and Serum Biochemical Response in Broiler Chickens

This study aimed to investigate the effects of Bacillus amyloliquefaciens LFB112 on the growth performance, carcass traits, immune response, and serum biochemical parameters of broiler chickens. A total of 396 1 day old, mixed-sex commercial Ross 308 broilers with similar body weights were allotted into six treatment groups. The assigned groups were the CON group (basal diet with no supplement), AB (antibiotics) group (basal diet + 150 mg of aureomycin/kg), C+M group (basal diet + 5 × 108 CFU/kg B. amyloliquefaciens LFB112 powder with vegetative cells + metabolites), C group (basal diet + 5 × 108 CFU/kg B. amyloliquefaciens LFB112 vegetative cell powder with removed metabolites), M group (basal diet + 5 × 108 CFU/kg B. amyloliquefaciens LFB112 metabolite powder with removed vegetative cells), and CICC group (basal diet + 5 × 108 CFU/kg Bacillus subtilis CICC 20179). Results indicated that chickens in the C+M, C, and M groups had higher body weight (BW) and average daily gain (ADG) (p < 0.05) and lower feed conversion ratio (FCR) (p = 0.02) compared to the CON group. The C+M group showed the lowest abdominal fat rate compared to those in the CON, AB, and CICC groups (p < 0.05). Compared to the CON group, serum IgA and IgG levels in the C+M, C, and M groups significantly increased while declining in the AB group (p < 0.05). B. amyloliquefaciens LFB112 supplementation significantly reduced the serum triglyceride, cholesterol, urea, and creatinine levels, while increasing the serum glucose and total protein (p < 0.05). In conclusion, B. amyloliquefaciens LFB112 significantly improved the growth performance, carcass traits, immunity, and blood chemical indices of broiler chickens and may be used as an efficient broiler feed supplement.

Evolution of irreversible somatic differentiation

A key innovation emerging in complex animals is irreversible somatic differentiation: daughters of a vegetative cell perform a vegetative function as well, thus, forming a somatic lineage that can no longer be directly involved in reproduction. Primitive species use a different strategy: vegetative and reproductive tasks are separated in time rather than in space. Starting from such a strategy, how is it possible to evolve life forms which use some of their cells exclusively for vegetative functions? Here, we develop an evolutionary model of development of a simple multicellular organism and find that three components are necessary for the evolution of irreversible somatic differentiation: (i) costly cell differentiation, (ii) vegetative cells that significantly improve the organism’s performance even if present in small numbers, and (iii) large enough organism size. Our findings demonstrate how an egalitarian development typical for loose cell colonies can evolve into germ-soma differentiation dominating metazoans.

Occurrence of Clostridium perfringens vegetative cells and spores throughout an industrial production process of black soldier fly larvae (Hermetia illucens)

The main use of black soldier fly larvae (Hermetia illucens) is currently as an animal feed ingredient. While the bacterial community of the larvae has been characterised repeatedly via sequencing, microbiological safety assessment based on culture-dependent techniques is still scarce. This study focused on the occurrence of the spore-forming foodborne pathogen Clostridium perfringens during rearing and consecutive processing of the larvae, based on observations in a single rearing facility. C. perfringens vegetative cells and spores were determined, in addition to total viable counts, total aerobic spore counts and intrinsic parameters including pH, water activity and moisture content. All samples were obtained from an industrial production plant. In a preliminary experiment, substrate ingredients and dried larvae were analysed, but the larvae were produced with a previous batch of the substrate mixture. A second, more detailed, experiment was performed where all samples were collected sequentially from the same production run (substrate ingredients, substrate mixture, starting larvae, harvested larvae, residue, dried larvae and stored dried larvae). In the two experiments, (presumptive) C. perfringens, as determined on tryptose sulphite cycloserine agar, was found at low numbers in the ingredients and in the second experiment it was also found in the substrate mixture. Over the two experiments, total C. perfringens counts (i.e. vegetative cells plus spores) ranged between 3.0±0.1 and <1.2±0.5 log cfu/g and C. perfringens spores ranged between 2.5±0.1 and <1.0±0.0 log cfu/g. Interestingly, vegetative cells and spores of C. perfringens were below the detection limit in all larvae samples. Therefore, it appears that at this production site and based on the samples investigated, the pathogen did not colonise the larvae. However, these results indicate that insect producers should monitor this pathogen among others, and install good hygiene practices to avoid contamination.

The Formation of Spore-Like Akinetes: A Survival Strategy of Filamentous Cyanobacteria

Some cyanobacteria of the order Nostocales can form akinetes, spore-like dormant cells resistant to various unfavorable environmental fluctuations. Akinetes are larger than vegetative cells and contain large quantities of reserve products, mainly glycogen and the nitrogen storage polypeptide polymer cyanophycin. Akinetes are enveloped in a thick protective coat containing a multilayered structure and are able to germinate into new vegetative cells under suitable growth conditions. Here, we summarize the significant morphological and physiological changes that occur during akinete differentiation and germination and present our investigation of the physiological function of the storage polymer cyanophycin in these cellular processes. We show that the cyanophycin production is not required for formation and germination of the akinetes in the filamentous cyanobacterium <i>Anabaena variabilis</i> ATCC 29413.

Reinstatement of Indian Ocean Porolithon coarctatum and P. gardineri based on sequencing type specimens, and P. epiphyticum sp. nov. (Corallinales, Rhodophyta), with comments on subfamilies Hydrolithoideae and Metagoniolithoideae

Partial rbcL sequences were obtained from the type specimens of Lithophyllum coarctatum and L. gardineri. Both species were variably assigned to either Hydrolithon or Porolithon during the last two centuries, with L. coarctatum, from the tropical eastern Indian Ocean currently considered a synonym of L. gardineri from the tropical western Indian Ocean. Phylogenetic analyses show that both belong in Porolithon and that they are distinct species despite their morpho-anatomical similarities, including a columnar morphology. Porolithon epiphyticum sp. nov., from the same locality as P. coarctatum, Cocos-Keeling Islands, is the first reported epiphytic species in the genus. Eight of the currently recognized 15 species of Porolithon have had their type specimens sequenced to correctly apply names, including the generitype specimen. DNA sequencing provides independent confirmation that the morpho-anatomical character of the presence of horizontal fields of trichocytes without intervening vegetative cells is diagnostic for Porolithon. The generitypes of the four genera classified in the subfamily Metagoniolithoideae, Dawsoniolithon, Floiophycus, Harveylithon, and Metagoniolithon as well as Hydrolithon in the subfamily Hydrolithoideae, have not been sequenced. The taxonomic and nomenclatural uncertainties in each of these genera are discussed.