Regular, Non-Sporing Gram-Positive Rods PDF

Regular, non-sporing Gram- Positive Rods By Prof. Ehab kheadr Prof. Nassra Dabour Section 14: this section comprises seven very different genera (Lactobacillus, Erysipelothrix, Brochothrix, Listeria, Kurthia, Caryophanon and Renibacterium) The most important genera...

Regular, non-sporing Gram- Positive Rods By Prof. Ehab kheadr Prof. Nassra Dabour Section 14: this section comprises seven very different genera (Lactobacillus, Erysipelothrix, Brochothrix, Listeria, Kurthia, Caryophanon and Renibacterium) The most important genera are: Genus: Lactobacillus Genus: Listeria  Genus Lactobacillus (Lb.) Morphology: Cells varying from long and slender, sometimes bent rods to short coryneform coccobacilli, chain formation common. Motility uncommon, nons-poring, gram-positive Some strains exhibit bipolar bodies, internal granulations or a barred appearance with the Gram- reaction or methylene blue stain. Metabolism fermentative: At least half of end product carbon is lactate. Lactate is usually not fermented. Additional products may be acetate, ethanol, CO2, format or succinate. Volatile acids with more than two carbon atoms are not produced. Microaerophilic: Surface growth on solid media generally enhanced by an aerobiosis or reduced oxygen pressure and 5-10% CO2, Some are anaerobes on isolation. Further description information: Pigment production rare, if present, yellow or orange - to- rust or brick red. Complex nutritional requirements for amino acid, peptides, nucleic acid derivatives, vitamins, salts, fatty acids and fermentable carbohydrates. Growth temperature range 2 - 53°C, optimum generally 30 - 40°C. Aciduric, optimal pH usually 5.5-6.2, the growth rate is often reduced at neutral or initially alkaline reactions. The DNA mol% G + C ranges from 32-53.  Lactobacillus was split up into 25 different genera in April 2020. Publisher in International Journal of Systematic and Evolutionary Microbiology Current name New name Lactobacillus casei Lacticaseibacillus casei Lactobacillus paracasei Lacticaseibacillus paracasei Lactobacillus rhamnosus Lacticaseibacillus rhamnosus Lactobacillus plantarum Lactiplantibacillus plantarum Lactobacillus brevis Levilactobacillus brevis Lactobacillus salivarius Ligilactobacillus salivarius Lactobacillus fermentum Limosilactobacillus fermentum Lactobacillus reuteri Limosilactobacillus reuteri Lactobacillus kefiri Lentilactobacillus kefiri Lactobacillus acidophilus Unchanged Lactobacillus delbrueckii subsp. bulgaricus Unchanged (aka Lactobacillus bulgaricus) Lactobacillus lactis Lactobacillus delbrueckii subsp. lacis Lactobacillus crispatus Unchanged Lactobacillus gasseri Unchanged Lactobacillus johnsonii Unchanged Lactobacillus helveticus Unchanged Lactobacilli versus milk and dairy products Milk contains no lactobacilli when it leaves the udder, but becomes very contaminated with lactobacilli by dust, dairy equipments, etc. Since streptococci grow faster, the number of lactobacilli remain low even in spontaneously soured milk, only after prolonged incubation do lactobacilli take over, due to their higher acid tolerance.  Lb. helveticus traditionally used in starters for the production of Swiss cheese and other types of hard cheeses, (e.g. Grana, Gorgonzola and Paramesan). In cheeses with ripening periods longer than about two weeks several mesophilic lactobacilli (Lb. plantarum (Lactiplantibacillus plantarum), Lb. brevis, (Levilactobacillus brevis) Lb. casei (Lacticaseibacillus casei), etc.) originating from the milk or the dairy environment reach level as high as 106-108 CFU/g cheese.  Lactobacilli for the production of fermented milks are Lb. delbrueckii subsp. bulgaricus, a component of the yoghurt flora, and Lb. kefir (Lentilactobacillus kefiri) the hetero-fermentative component of the kefir. Several species of lactobacilli may contribute to spoilage of dairy products by slime or gas production, only two species cause specific spoilage. Lb. maltaromicus responsible for malty flavour in milk and Lb. bifermentans has been found to cause the blowing of Edam cheese.  Lactobacillus delbruechii Rods with round ends, by about 2-9 µm, occurring singly and short chains, good growth at 45°C or even at 48-52°C. The mol% G + C of the DNA is 49–51. Three subspecies are presently recognized Lactobacillus delbrueckii subsp. delbrueckii Isolated mainly from plant material fermented at high temperatures (40–53°C). Its nutritive requirements are complex, Lactobacillus delbrueckii subsp. bulgaricus (until 1984 known as Lactobacillus bulgaricus) Lactobacillus delbrueckii subsp. bulgaricus is commonly used alongside Streptococcus thermophilus (Str. Thermophilus) as a starter for making yogurt. The two species work in synergy, with Lb. bulgaricus producing amino acids from milk proteins, which are then used by Str. thermophilus.  Both species produce lactic acid which gives yogurt its acid flavor and acts as a preservative. The resulting decrease in pH also partially coagulates the milk proteins (casein), resulting in yogurt's thickness. While fermenting milk, Lb. bulgaricus produces acetaldehyde, one of the main yogurt aroma components.  Some strains of Lb. bulgaricus also produce bacteriocins, which have been shown to kill undesired bacteria in vitro. It is often helpful to sufferers of lactose intolerance whose digestive systems lack the enzymes to break down lactose to simpler sugars. It has also been considered a contaminant of beer due its homo-fermentatative production of lactic acid, an off-flavor in many styles of beer.  In other styles of beer, however, lactic acid bacteria can contribute to the overall appearance, aroma, taste, and/or mouthfeel, and generally produce an otherwise pleasing sourness. Lactobacillus delbrueckii subsp. lactis Thermophilic bacteria with optimum temperature of 40-45°C, homo-fermentative, It is a part of starters named thermophilic starters, which used in hard cheeses such as Swiss and Italian cheeses.  Lactobacillus acidophilus Lactobacillus acidophilus (Latin meaning acid-loving milk-bacterium) is a homo-fermentative species. It grows readily at rather low pH values (below pH 5.0). It has an optimum growth temperature of around 37°C. Lb. acidophilus occurs naturally in the human and animal gastrointestinal tract and mouth.  Strains of Lb. acidophilus may be considered to have probiotic characteristics. These strains are commercially used in many dairy products, sometimes together with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in the production of acidophilus-type yogurt. ‘probiotic’ was defined in 2001 by an the Food and Agricultural Organization of the United Nations and the World Healt Organization (FAO/WHO).“Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”  acidiophilus probiotic effects A blend of bacterial strains including Lb. acidophilus NCFM decreased the incidence of pediatric diarrhea. At adequate daily feeding levels, Lb. acidophilus may facilitate lactose digestion in lactose-intolerant subjects. A study found that feed supplemented with Lb. acidophilus L1 and fed to cattle resulted in a 61% reduction of Escherichia coli O157:H7. Research has indicated Lb. acidophilus may be helpful reducing serum cholesterol levels.  Lb. acidophilus LA-5 produces bacteriocin CH5 that is both antibacterial and inhibitory against certain yeasts and molds and is effective against both Salmonella typhimurium and Campylobacter jejuni. Anti-inflammatory effects have also been observed in people consuming Lb. acidophilus NCFM. Additionally Lb. acidophilus LA-5 has shown to inhibit growth of breast cancer cells, and positive effects on chemotherapy patients. An improvement of lipid metabolism has also been linked to Lb. acidophilus LA-5.  Lactobacillus helveticus Thermophilic bacteria can grow with temperature up to 50-52°C. It is most commonly used in the production of American Swiss cheese and Emmental cheese, Sometimes it used in making other styles of cheese, such as Cheddar, Parmesan, Romano, Provolone, and Mozzarella.  The primary function of Lb. helveticus culture is to prevent bitterness and produce nutty flavors in the final cheese. In Emmental cheese production, Lb. helveticus is used in conjunction with a Propionibacter culture, which is responsible for developing the holes (known as "eyes") through production of carbon dioxide gas.  Lactobacillus casei (Lacticaseibacillus casei) ‫ة‬XY MZ[T X\]^‫ و‬Mesophilic starter ‫ت‬MN‫د‬MPQ‫ ا‬ST J‫ وھ‬USA JK : MZ[T subsp a- Lacticaseibacillus casei subsp. casei. b- Lacticaseibacillus casei subsp. pseudofantorum. c- Lacticaseibacillus casei subsp. rhaminosus. d- Lacticaseibacillus casei subsp. tolerance.  Lacticaseibacillus casei is typically the dominant species of nonstarter lactic acid bacteria (NSLAB) present in ripening Cheddar cheese It has high proteolytic activity and used in many mesophilic starters. Lactobacillus plantarum (Lactiplantibacillus plantarum) Lactiplantibacillus plantarum is a widespread member of the genus Lactobacillus, Commonly found in many fermented food products ( fermented sausages, stockfish, brined olives….) as well as anaerobic plant matter. It has the ability to liquefy gelatin.  This organism considered an ideal candidate for the development of probiotics. Lactiplantibacillus plantarum has been applied to reduce the allergenicity of soy flour. The ability of Lactiplantibacillus plantarum to produce antimicrobial substances helps them survive in the gastro- intestinal tract of humans. The antimicrobial substances produced have shown significant effect on Gram- positive and Gram-negative bacteria.  Genus: Listeria All species within the Listeria genus are Gram- positive, non-sporeforming, catalase-positive rods. The genus Listeria currently contains ten species: L. fleischmannii, L. grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. rocourtiae, L. seeligeri, L. weihenstephanensis and L. welshimeri.  Listeria can be found in soil, which can lead to vegetable contamination, animals can also be carriers. Listeria has been found in uncooked meats, uncooked vegetables, fruit such as cantaloupes, pasteurized or unpasteurized milk, foods made from milk, and processed foods.  Pasteurization and sufficient cooking kill Listeria; however, contamination may occur after cooking and before packaging Under the microscope, Listeria species appear as small, Gram-positive rods, which are sometimes arranged in short chains. In direct smears, they may be coccoid, so they can be mistaken for streptococci. Longer cells may resemble corynebacteria. Flagella are produced at room temperature, but not at 37°C.. Named after the English pioneer of sterile surgery Joseph Lister, the genus received its current name in 1940. The major human pathogen in the Listeria genus is L. monocytogenes. It is usually the causative agent of the bacterial disease, listeriosis, a serious infection caused by eating food contaminated with the bacteria.  listeriosis affects primarily pregnant women, newborns, adults with weakened immune systems, and the elderly. Listeriosis is a serious disease for humans; the overt form of the disease has a mortality rate of about 20 percent.  Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea, may precede more serious forms of listeriosis or may be the only symptoms expressed. The onset time to serious forms of listeriosis is unknown, but may range from a few days to three weeks Invasive infection by L. monocytogenes. Listeria monocytogenes as they appear when grown on Listeria-selective agar